(CNN) -- The International Committee of the Red Cross is trying to negotiate a cease-fire between Syrian authorities and the opposition so the humanitarian agency can deliver food and medical supplies to the besieged city of Homs and other locations, a spokesman said Monday.

Negotiations are "happening now," said Bijan Farnoudi, a spokesman for the ICRC in Geneva, Switzerland.

"We have been in Syria for a while now, based in Damascus, so we want to reach some of the hardest-hit areas," he said. "We have been to some places like Homs and so on from time to time, but it is very crucial to have a cessation of fire to provide humanitarian services."

Meanwhile, President Barack Obama's top military adviser said it is premature to aid in arming the Syrian opposition, reinforcing the belief of a rebel commander that the uprising is an "orphan revolution" without the international support prevalent in other Arab Spring revolts.

The claim follows opposition reports Monday that Syrian forces began a 17th day of shelling of opposition strongholds in Homs.

The opposition Local Coordination Committees of Syria said at least 18 people had been killed across the country Monday, including 13 in Homs -- among them a whole family made up of three women and a young man. The group also said security forces fired tear gas at demonstrators around the university in the city of Aleppo.

The opposition network estimates almost 9,000 people have been killed since the start of the uprising.

Elsewhere in the country, hundreds of protesters marched through the heart of Damascus on Monday, just steps from security buildings in a bold show of strength, the LCC said. Thirty people were detained in the central Damascus neighborhood of Kafarsouseh, it said.

Demonstrators in the capital blocked a main road with burning ties, said Ahmed, a protester, who characterized the action as "a big thing."

"This is part of our resentment against the regime," he said.

In Hama, government forces stormed various neighborhoods and erected checkpoints, according to the Syrian Observatory for Human Rights, another opposition group. Snipers took up positions inside a building under construction to monitor movements in the neighborhood of Hamidiya, it said.

Meanwhile, state media reported two soldiers were killed and one was wounded in a clash with "armed terrorists" near Hama. Funeral services were held Monday for 12 security workers killed throughout the country, the state-run Syrian Arab News Agency said.

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CNN cannot independently verify opposition or government reports of casualties.

Diplomatic efforts have all but failed to end the brutal crackdown, with two powerful nations -- China and Russia -- vetoing a U.N. Security Council resolution calling on President Bashar al-Assad's to relinquish power, and the Arab League suspending an observer mission amid escalating violence.

Representatives from various countries are expected to meet in Tunisia this week to discuss the conflict.

"The goal of this conference is to increase pressure on the Syrian regime. There are indications coming especially from China, and to some extent from Russia that there may be a change in position," Arab League Secretary General Nabil Elaraby told reporters Monday.

In one rural village in the north, farmers, carpenters and university students are among the face of the opposition, according to CNN's Ivan Watson, one of the few reporters in Syria, whose government has placed strict restrictions on international journalists and refused many of them entry.

Watson said the men of village of Binnish describe themselves as members of the rebel Free Syria Army, "but it would be much more accurate to call them an impromptu village guard. Many of them are defending the olive groves that surround their community, with little more than hunting shotguns."

The rebel commander in Binnish -- who defected from the Syrian army six months ago -- said the men don't have enough guns or ammunition.

He called the Syrian uprising an "orphan revolution" because unlike the revolt in Libya, the Syrian rebels have not received foreign support.

Like many members of the opposition, the commander covered his face during the interview to hide his identity out of fear of reprisals by Syrian forces.

There has been a growing call among some in the international community to arm the opposition, best described as a network of faceless activist and opposition groups that include a loosely organized rebel army and militias.

But not everyone, including the United States, is in agreement.

"I think it's premature to make a decision to arm the opposition movement in Syria, because I would challenge anyone to clearly identify for me the opposition movement in Syria at this point," Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said Sunday on CNN's "Fareed Zakaria GPS."

Dempsey, an Army general who served two tours of duty in Iraq, warned that Syria is "an arena right now for all of the various interests to play out."

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Those interests include neighbors such as NATO ally Turkey; the region's Sunni and Shiite Muslim powers, Saudi Arabia and Iran, which is Syria's leading ally; and al Qaeda, the terrorist network that has shown signs of interest in the conflict, he said.

"There's a number of players, all of whom are trying to reinforce their particular side of this issue. And until we're a lot clearer about, you know, who they are and what they are, I think it would be premature to talk about arming them," Dempsey said.

Sen. John McCain of Arizona said Monday he believes "there should be no option left off the table."

"The massacre goes on," McCain said. "There's risk of stalemate. ... There's lots of ways of getting weapons and assistance to the resistance there besides U.S. direct shipment of arms. There's a contact group that the U.S. is joining with in Tunisia this Friday. And I believe they need medical, technical, all kinds of assistance, and every option should be on the table, including a way to get weapons to them."

He noted the United States previously intervened in Bosnia-Herzegovina and in Kosovo because "massacres were taking place."

Sen. Lindsey Graham of South Carolina, who is with McCain in Cairo, said Monday he believes it's in Americans' best interest to break Syria away from Iran.

"I do believe that al Qaeda tries to fill vacuums wherever they exist, but I don't buy the narrative that the Syrian people are risking their lives ... to become a branch of al Qaeda," he said.

Graham said he believes "the idea of trying to arm the opposition forces needs to be considered, very much considered, and at the end of the day, what happens in Syria really can change the course of the Mideast."

Syria's uprising began in March amid the "Arab Spring" demonstrations, when longtime autocrats fell in Tunisia and Egypt and other nations found themselves battling popular revolts.

Syria's government responded by unleashing police and troops on anti-government protesters calling for more political freedoms, a movement that quickly spiraled into the opposition calling for al-Assad's ouster. The president has blamed "terrorists" and foreigners for threatening the stability of Syria.

Nearly all other reports from within the country, however, tell a different story.

Amateur video and opposition reports released via social media and telephone calls from Homs have documented 17 days of bombardment, with explosions from mortars and tank shells launched by Syrian forces every few minutes, people bleeding to death in the streets for lack of medical attention, and snipers picking off civilians running for cover.