Syrian forces on Wednesday attacked rebel bastions as UN chief Ban Ki-moon urged President Bashar al-Assad to immediately implement a UN-Arab League peace plan he has reportedly accepted.
As the United States accused the Syrian leader of failing to fulfill a pledge to respect the plan, senior US senators went a step further, filing a resolution calling for the opposition to be armed.
In Baghdad, even as Arab foreign ministers thrashed out a resolution on Syria to be debated at a landmark Arab League summit on Thursday, Damascus made it clear it would not abide by any of its initiatives.
On the ground, at least 21 people were killed as Syrian forces backed by tanks attacked the central town of Qalaat al-Madiq and other areas Wednesday, the Syrian Observatory for Human Rights said.
Ban, the United Nations secretary general who is to attend the Arab summit in Baghdad, expressed deep concern at the continued bloodshed, which the UN says has claimed more than 9,000 lives in the past year.
While he welcomed Syria's acceptance of the six-point plan put forward by the UN-Arab League envoy Kofi Annan as an "important initial step" towards ending the killing, he urged Assad "to put commitments into immediate effect.
"There is no time to waste," he stressed.
Ban said he would meet key Arab leaders in Baghdad to discuss how the UN and Arab League states could work together to implement the six-point plan.
In Baghdad, Iraqi Foreign Minister Hoshyar Zebari said Wednesday on the eve of the Arab summit that the meeting would stop short of calling for Assad to quit or discuss arming his foes.
A copy of the draft resolution being debated by Arab foreign ministers urges the Syrian regime to halt the violence, protect civilians and guarantee the right to demonstrate peacefully.
The text, obtained by AFP, also calls on the Syrian government and all opposition factions "to deal positively with the envoy (Annan) by starting serious national dialogue."
But Syrian foreign ministry spokesman Jihad Makdissi said Damascus would pay no heed.
"Syria will not cooperate with any Arab League initiative at any level," he said.
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The 22-member pan-Arab body in November voted at an extraordinary meeting to suspend Syria until Assad implements an Arab deal to end his government's year-long crackdown on dissent.
Qatar, which had pushed for a harder line against Assad, said it was sending a low-level representative to the Baghdad summit in a show of displeasure at the line taken by its Iraqi hosts.
In Washington, US State Department spokeswoman Victoria Nuland said Assad had not taken the necessary steps to implement the peace plan crafted by Annan, a former UN secretary general.
The United States was concerned over "arrests and violence continuing in Syria today," Nuland told reporters, vowing to "keep the pressure" on the Syrian leader.
"We will judge him on his actions, not his promises," she added, echoing comments made Tuesday by Secretary of State Hillary Clinton.
Senior US lawmakers went a step further.
Republican Senator John McCain presented a toughly worded text co-sponsored by four other senators including Lindsey Graham and independent Joe Lieberman condemning "the mass atrocities committed by the government of Syria" and backing the right of the Syrian people to defend themselves.
The non-binding resolution backed calls by some Arab leaders "to provide the people of Syria with the means to defend themselves against Bashar al-Assad and his forces, including through the provision of weapons and other material support."
Annan said on Tuesday that Assad's government had accepted his plan, which includes a commitment to stop all violence, daily two-hour humanitarian ceasefires and media access to all areas affected by the fighting.
It also calls for an inclusive Syrian-led political process, the right to demonstrate, and the release of people detained arbitrarily.
China and Russia urged both sides to honour commitments to halt the armed conflict.
Moscow called on the Syrian opposition to "follow the example" of the Damascus regime in supporting Annan's mediation efforts to stop the bloodshed.
Shelling killed four civilians, while five rebel fighters and four soldiers died in fierce clashes in Qalaat al-Madiq and surrounding villages, the Syrian Observatory for Human Rights said.
The army tried to storm other rebel positions across the country, including northwest Idlib, central Homs and the southern province of Daraa, the Britain-based monitoring group said.
Troops entered the town of Qalaat al-Madiq, in Hama province, just after dawn following a 17-day barrage of shelling and heavy gunfire to root out rebels, but did not have full control of the town, it said.