Syrian activists have said they will "fight until the last person" as columns of tanks and armoured vehicles prepared to mount a ground assault on the embattled city of Homs.
But even as security forces shelled Homs for a 17th consecutive day, the International Committee of the Red Cross (ICRC) said it was negotiating a ceasefire.
The ICRC said it was working to allow aid and medical equipment to be delivered to the worst-affected regions, but did not give details on who is involved in the talks.
"[We are] exploring several possibilities for delivering urgently needed humanitarian aid", Saleh Dabbakeh, a Red Cross spokesman, told Al Jazeera.
"These include the cessation of fighting in the most affected areas to facilitate swift Syrian Arab Red Crescent and ICRC access to the people in need."
"The content of the discussions with the Syrian authorities and all those involved in the fighting remains confidential," he added.
In the capital Damascus on Tuesday there were also reports of government forces firing into crowds of protesters, wounding at least four people.
News agency reports said that the troops were using live ammunition.
In Homs evidence emerged online of shelling early on Tuesday morning, with reports of up to 12 people being killed and more than 100 wounded.
Activists said that an additional 16 people were killed in the country on Monday, with dozens more injured.
Government tanks were reported to be stationed in the Inshaat area of Homs, directly opposite the Baba Amr neighbourhood where the shelling has so-far been concentrated. Activists fear a direct ground assault, which the poorly-armed opposition would be unlikely to repel.
Reuters said that around 60% of Baba Amr's population of 100,000 had fled from the city.
Videos posted on YouTube purported to show shells falling in Homs and damaged houses. Another video gave viewers a tour of the wreckage of a family home destroyed in the bombing.
Live footage broadcast on Bambuser.com showed glimpses of smoke and the sound of shelling and intermittent gunfire.
One activist told the Associated Press that the residents would fight "until the last person" to repel President Bashar al-Assad's forces.
Meanwhile Tunisia has said that an agreement that Syria should not be invaded by foreign troops was reached on Monday by foreign ministers at a meeting in Rome.
"We don't want an Iraqi scenario," said Rafik Abdessalem, Tunisia's foreign minister.
He added: "we have to preserve the integrity of Syria."
Abdessalem said a meeting will be held in Tunis to work towards an end to the violence, and that opposition groups including the Syrian National Council will attend.
American senator John McCain, the former Republican presidential candidate, repeated calls for the Free Syrian Army to be armed in order to mount a defence against President Assad's forces.
"It is time we gave the [opposition] the wherewithal to fight back and stop the slaughter," McCain said in Cairo on Monday.