The Red Cross will try to evacuate hundreds of civilians trapped by fierce fighting in Homs, as violence killed dozens of people across Syria.
The head of the UN Supervision Mission in Syria, meanwhile, told the UN Security Council of the intensifying violence in the country but said the nearly 300 unarmed monitors were "morally obliged" to stay.
"We are going nowhere," Major General Robert Mood said after the closed meeting.
On the political front, Russia resisted Western pleas to help remove Syria's President Bashar al-Assad from power despite the escalating hostilities that have battered a UN-backed peace initiative.
"We believe that nobody has the right to decide for other nations who should be in power and who should not," Russian President Vladimir Putin said after a G20 summit in Mexico.
The US State Department said Secretary of State Hillary Clinton would meet her Russian counterpart Sergei Lavrov in Saint Petersburg next week, as the two sides struggle to find a common stance to end the conflict.
Violence on Wednesday killed more than 60 people, more than a third of them government troops, the Syrian Observatory for Human Rights said, as an activists spoke of a "desperate" situation in and around Homs.
"Every day there are many wounded from the shelling, and we can't do anything for them because we have nothing to treat them with," activist Abu Bilal told AFP in Beirut via Skype.
"The shelling is practically constant, and we can't get anybody out of the besieged districts," he added.
Last week the Observatory said more than 1000 families were stuck in the region around Homs and spoke of dozens of people wounded in urgent need of medical care.
"Electricity has been cut off for four days" in the Old City of Homs and "there's no more flour to bake bread. There really is nothing to eat," said Abu Bilal.
The International Committee of the Red Cross said it was hoping to evacuate civilians stranded in Homs city and bring in relief aid and medical supplies with the help of the Syrian Arab Red Crescent.
The ICRC said it had made a request for a temporary halt in fighting on Tuesday to the government and opposition groups. Both parties said they would respect the pause.
"Our first priority, together with the Syrian Arab Red Crescent, is to evacuate the wounded and the sick to safer areas, where they can be treated," said the ICRC's Beatrice Megevand-Roggo.
The Red Cross and the Red Crescent are ready to enter several Homs city neighbourhoods, including the battered districts of Khaldiyeh and Jourat al-Shiah, which activists say have been pounded mercilessly for days.
Homs has been under intermittent attack by regime forces ever since its Baba Amr neighbourhood was relentlessly pounded for a month earlier this year and the regime retook it from rebels.