(CNN) -- The conflict in Libya has at times seemed as much a war of words as a war on the ground, with both the Gadhafi government and the rebel forces claiming to hold the upper hand. But could reports of significant rebel advances in recent days signal a decisive shift in momentum to their side, after months of apparent stalemate?

Col. Roland Lavoie, a spokesman for NATO's military operation, told reporters Tuesday that "anti-Gadhafi forces are now assuming control of the key approaches to Tripoli," the Gadhafi-held capital which has long eluded the rebels' grasp.

Describing the advances as "the most significant anti-Gadhafi territorial gain we have seen in months," he painted a picture of Gadhafi's forces on the back foot, losing "considerable grounds" on several fronts, as the rebels advance into the west.

NATO deputy spokeswoman Carmen Romero also spoke of the use by government forces of an unguided short-range ballistic missile in a civilian area as a sign that "Gadhafi and his regime are desperate."

And an impassioned audio address by Libyan leader Moammar Gadhafi earlier this week in which he called on his people to "be ready to fight to liberate our pure and good land" could suggest he is under mounting pressure.

The rebels themselves say they are now poised to seize the key town of al-Zawiya, which lies on a strategic supply route about 30 miles (50 kilometers) to the west of Tripoli, and then to advance on the capital within days.

Supporters outside the North African country are similarly optimistic. Dr. Mahmoud Traina, a 31-year-old Libyan-American cardiologist in southern California, called the rebel push into Zawiya in recent days "a turning point," since Gadhafi had fought hard to maintain control of the coastal city.

"It shows the weakening of his regime," Traina, who was born in the Untied States but has family in Tripoli and Misrata, told CNN in a telephone interview. "It cuts off his supply routes for his last remaining supply of fuel, and cuts supply lines for all products from Tunisia."

He added: "I think this is the end-game move before he's out of power. At this point, it's only a matter of time."

But whether such hopes are well-founded is up for debate. Representatives of the Gadhafi government still maintain that it is doing well -- and analysts differ over what might happen next.

Professor Malcolm Chalmers, a UK defense policy expert at the Royal United Services Institute in London, believes the military momentum is now with the rebels, after a period in which they made no advances.

"This has always been a war of attrition by NATO, based on the view that over time the capabilities of the regime would continue to diminish and at some stage -- especially since Gadhafi's forces were having to fight on several fronts at once -- would start to crumble," he said. "And indeed, that seems to be what's happening."

The progressive degrading of Gadhafi's military capabilities by NATO strikes has levelled the playing field for the rebels, he said, who are also now benefiting from more access to funds.

"It's become more and more difficult for (Gadhafi's forces) to retake ground that they lose because their offensive weaponry is being destroyed, and their command and control ability is being destroyed," he said.

If rebel gains mean the regime forces also lose their re-supply routes from Tunisia, as seems likely, "that is going to accelerate the decline in military capability," Chalmers said, adding that he does not see them lasting "more than one or two months, maybe less."

However, Simon Henderson, a senior fellow at the Washington Institute for Near East Policy, told CNN it was still too early to say whether the end-game was in sight.

"There has been so much to-ing and fro-ing in terms of advance and retreat by both sides, it's hard to make the judgment at the moment that the opposition has made significant and permanent gains," he said.

"It's still too early to say that the end of this is going to be a complete defeat of Gadhafi's forces," he said, pointing to the fact that despite months of fighting the rebels have not managed to take Tripoli.

"It still seems as though Gadhafi is a long way from being pushed out," he said.

Senior U.S. officials also caution that the rebels made real advances in the first months of the campaign, only to lose them and for the situation to remain stagnant for a while.

The officials, who spoke to CNN on the condition of anonymity, say the current advances are "significant," but that it remains to be seen how long Gadhafi can hang on and what supplies he still has.

They say the end for Gadhafi's regime could be tomorrow, or could still be a long way off. Nobody really wants to predict when it might come, they say -- but it won't be until people in Tripoli sense the end is near and rise up.

Observers note that NATO action has been key to almost every significant gain the rebels have made so far in the five-month-old war -- and some question whether NATO is going beyond its mission of protecting the civilian population if it continues to target Gadhafi's forces when they are on the defensive.

Lavoie disputed that Tuesday, saying that the only side NATO took was "the side of the people of Libya" and that any targets hit were those that represented "a threat to the local population."

Although NATO says the rebels effectively control the territory around Tripoli, it is still by no means certain they can take the capital, a Gadhafi stronghold. After 42 years in power, the Libyan leader still commands the loyalty of many people and the city regularly witnesses large pro-Gadhafi rallies.

While the rebels have now held towns along the way to Zawiya for the past few days, they have not so far been able completely to take control of Zawiya itself.

And residents fleeing Tripoli told CNN they believed that if the rebels cannot coordinate an attack from several fronts they will struggle to succeed, as almost all roads in and out of the capital are shut or heavily monitored by government forces.

Nonetheless, Col. Ahmed Banni, military spokesman for the opposition National Transitional Council, said Tuesday that rebels hope to enter the capital by the end of the month.

Rebel commander Col. Radwan Heid struck a similar note of optimism. "These are the last days, God willing," he told CNN, referring to Gadhafi's grip on the capital and the country as a whole.

Morale among rebel troops in and around the western Nafusa mountains -- where NATO says local people feel safe enough from attacks by pro-Gadhafi forces to start to return -- also seems high, observers say.

But a spokesman for Gadhafi, Ibrahim Musa, offered a different view this week. He said the government was "doing very well" despite problems with "armed gangs" in the coastal towns of Surman and Sabratha, which NATO said rebel forces had reached.

"God willing, we are able to lead this battle successfully. We will achieve peace and victory," Musa said.

At a news conference Thursday, Libyan Prime Minister al-Baghdadi al-Mahmoodi said that the military is "powerful enough to finish this battle" to its advantage, but warned that the cost would be too high, calling again for dialogue to resolve the crisis peacefully rather than militarily.

Al-Mahmoodi said the government's call for a peaceful resolution comes from "a position of power, not weakness... we are able to continue the fight, but from the very beginning we chose peace." The government was currently in talks with all parties, he added.

If the rebels' military advances outstrip such diplomatic efforts, what might lie ahead for Libya?

Chalmers said that may hinge on whether people within the Gadhafi regime decide the game is up. "One very plausible scenario for the next stage is that there will be people within the regime other than the Gadhafi family who seek to negotiate a cease-fire and a political settlement which involves the Gadhafi family leaving in some shape or form, but doesn't involve a rebel military advance into Tripoli," he said.

However, political divisions within the rebel ranks make it hard to be confident that they can form a credible national government even if they do achieve a military victory over Gadhafi's government, Chalmers added.

The big worry over the next month, he said, is that the regime simply collapses, leaving the country to fall into a mess of tribal rivalries and reprisals against government supporters, with Islamist groups also getting involved. "It now looks as if the days of the Gadhafi regime itself are numbered, but who knows who will replace it?" he asked.

Henderson agrees that the rebel forces "still fail to impress." Their credibility was not improved by the murky killing last month of Gen. Abdul Fattah Younis in Benghazi, the city where the rebels' Transitional National Council (TNC) is based, he said.

"They are far from being a united front and after the death of Younis they are short of professional leadership," Henderson said.

Saad Djebbar, an international lawyer who negotiated the release in Scotland two years ago of Abdelbaset al-Megrahi, the man convicted of blowing up a Pan-Am flight over Lockerbie, believes it is vital to establish what he called a "coalition of cultures" which represents all regions, tribes and factions to ensure a stable Libya post-Gadhafi.

He called on the international community to facilitate that coalition because "Libyans don't have the expertise to do it" -- and told CNN Gadhafi is "losing power by the minute."

Omar Turbi, the Libyan-born president of a computer company who moved to the United States aged 18 and now lives in Laguna Beach, California, agrees that Gadhafi's grip on power is weakening.

The proximity of rebel forces to Gadhafi's power base in Tripoli "is a clear indication that he doesn't have any fighting or any kind of power to fight," he said.

Turbi, who says he works closely with the TNC in an unofficial capacity, said it planned efforts to prevent looting and reprisals once the Gadhafi regime falls.

He speculated that the Gadhafi government would last no more than 30 days. "We have a pretty strong feeling that something is up," he said. "Who knows? Maybe in a few days, things will start to crumble."

Looking ahead, he said he hoped that any new government would incorporate all elements of Libyan society except for those with blood on their hands.

"Everyone in Libya should be welcomed back to take part in building the country or keeping the country together."

Mansour El-Kikhia, 59, a Libyan scholar and dissident, also predicted Gadhafi's downfall within days. "He's going, he's going down," he said. "It's just a matter of time, that's all. I bet you, maybe 15 more days."

Born in Benghazi, he left in 1977 to study in the United States and is now an associate professor and chairman of the Department of Political Science and Geography at the University of Texas, San Antonio. Recently, he visited relatives in Libya he had not seen in three decades.

El-Kikhia predicted that Gadhafi will make any departure a messy one by firing missiles into oil fields in the rebel-held eastern reaches of the country and setting them afire.

And he warned that with the main supply route for Gadhafi's forces now closed, the humanitarian situation could rapidly worsen.

Already, people in Tripoli are having problems, as shops are having difficulty getting goods and foodstuffs. "It's turning into being a disaster," he said. "This really means that the rebels have to move fast."

CNN's Tom Watkins, Sara Sidner, Dave Gilbert, Elise Labott and Jomana Karadsheh contributed to this report.