Syrian tanks bombarded opposition areas in Homs overnight and the Red Cross tried for a sixth day to gain access to Baba Amr, a fallen rebel stronghold where activists have reported bloody reprisals by President Bashar al-Assad's forces.
President Barack Obama said it was only a matter of time before Assad left office, describing Syria's turmoil as "heartbreaking and outrageous," but opposed a call by a senior U.S. senator for American military action to force him out.
No independent witnesses have been allowed into Baba Amr since troops retook it on Friday after a four-week siege, increasing concern about the fate of about 4,000 civilians estimated to have remained in the shattered neighborhood.
Local opposition activists said troops and pro-Assad militiamen occupying Baba Amr had killed seven males, including a 10-year-old, from the Berini family with knives. "They were stabbed to death yesterday. Their bodies were dumped in farmland next to Baba Amr," Mohammed al-Homsi told Reuters.
Syria imposes severe media restrictions, making such reports hard to verify, although the United Nations has compiled evidence of abuses it says amount to crimes against humanity.
The International Committee of the Red Cross said an aid convoy destined for Baba Amr had been awaiting permission to enter since Friday. "We have not made it in," the ICRC's Damascus-based spokesman Saleh Dabbakeh said.
The world has found no way to halt a year of bloodshed since many Syrians rose against Assad in what has proved the longest and bloodiest of Arab revolts against entrenched rulers.
At the United Nations, the five permanent Security Council members and Morocco met on Tuesday to discuss a U.S.-drafted resolution urging an end to the Syrian government's crackdown on demonstrators, a text some Western envoys said was too weak.
Russia and China, adamantly opposed to any Libya-style intervention in Syria, have vetoed two previous draft measures that would have condemned Damascus and it is not clear whether the latest one stands any chance of success.
According to a text seen by Reuters, the U.S. draft demands "unhindered humanitarian access" and "condemns the continued widespread, systematic, and gross violations of human rights and fundamental freedoms by the Syrian authorities."
AMOS'S DELAYED VISIT
Top U.N. humanitarian official Valerie Amos, denied entry to Syria last week, was due there on Wednesday. Former U.N. chief Kofi Annan plans his first visit to Damascus as joint envoy of the United Nations and the Arab League on Saturday.
Diplomacy has yet to brake a conflict likely to have cost more than 10,000 lives: the United Nations said security forces had killed well over 7,500 people and Syria said in December that "terrorists" had killed more than 2,000 security personnel.
Assad, who has promised a multi-party parliamentary election in May, told a visiting Ukrainian lawmaker that the power of any state lay in popular support and that Syrians had proved they would pursue reforms and "confront terrorism backed by foreign sides," the state news agency SANA reported on Wednesday.
Apart from the shelling of the Homs districts of Karm al-Zeitoun, Jub al-Jandali and Deir Baalba, opposition sources said Syrian troops had staged raids in the towns of Qara and Yabroud north of Damascus, and in the northern city of Aleppo.
The White House said Obama was committed to diplomacy to end the violence, saying Washington wanted to isolate Assad, cut off his sources of revenue and encourage unity among his opponents.
"Ultimately this dictator will fall," Obama said, while rejecting a call by Senator John McCain for a U.S.-led effort to protect Syrian civilians with air strikes on Assad's forces.
"For us to take military action unilaterally, as some have suggested, or to think that somehow there is some simple solution, I think is a mistake," the president said.
Assad can still count on powerful allies such as Russia and China, as well as others such as Iran, Venezuela and Cuba.
China sent Li Huaxin, its former ambassador in Syria, to Damascus this week and SANA said he had reiterated Beijing's "opposition to interference in Syrian internal affairs."
However, China is bringing workers home from Syria in an apparent attempt to avoid a repeat of last year's rescue of its nationals from Libya due to violence there.
Only about 100 Chinese workers will be left behind to guard work camps and equipment, Commerce Minister Chen Deming said, without saying how many Chinese workers would be repatriated.
(Additional reporting by Oliver Holmes in Beirut, Louis Charbonneau at the United Nations, Lucy Hornby and Aileen Wang in Beijing and Tabassum Zakaria in Washington; Writing by Alistair Lyon; editing by Janet McBride)