Syrian troops shelled villages, fired across frontiers and were accused of massacres in the hours before a deadline on Tuesday that many doubt can usher in a U.N.-brokered ceasefire and halt a 13-month slide into all-out civil war.
Diplomats trying to contain a crisis that has inflamed the Middle East and pitched old Cold War rivals into opposing camps will not wish to abandon their most comprehensive peace plan yet. The plan's author, international envoy Kofi Annan, visits Turkey and Iran on Tuesday, while Russia hosts the Syrian foreign minister.
In Damascus, President Bashar al-Assad said nothing on Monday about whether he would honour his undertaking to Annan to start withdrawing government forces from urban areas on April 10 - a deadline that diplomats say appears to give him until midnight Syrian time, or 2100 GMT, on Tuesday to comply.
Assad's demand on Sunday for written guarantees of good faith from the rebels - which their leaders rejected out of hand - as well as the hostile actions of Syrian troops on the ground, fuelled doubts that Annan's schedule for the full truce to start by 6 a.m. (0300 GMT) on Thursday, April 12, would be respected.
Syria was to have started pulling troops out of towns and cities by Tuesday to pave the way for a ceasefire to start 48 hours later.
April 10 has become void, concluded Turkish Deputy Foreign Minister Naci Koru. Ankara, Assad's former ally and now a foe, deplored shooting that wounded five people in a refugee camp inside Turkey - in the border area which Annan, the former U.N. secretary-general, is expected to visit on Tuesday.
Another neighbour, Lebanon, condemned the killing of a local journalist by Syrian soldiers firing over the border.
In Washington, State Department spokeswoman Victoria Nuland said: These incidents are just another indication that the Assad regime does not seem at all willing to meet the commitments that it made to Kofi Annan.
She derided Assad's new condition for a truce as chaff to stall for time and said there was no indication of his forces preparing to withdraw.
Opposition activists in Idlib province, near the Turkish border, accused troops of mounting an offensive that had killed dozens this week, including young men rounded up and executed. Other anti-Assad groups said the army shelled a village near the central city of Hama, killing 30 people, including women and children.
The world gave Assad a deadline, said activist Mohammad Abdallah. But he sees it as an opportunity.
The United Nations says Syrian forces have killed 9,000 people in 13 months, while Assad's government says rebels have killed more than 3,000 soldiers and security personnel.
Government curbs on the media limit independent reporting from inside Syria.
U.N. Secretary-General Ban Ki-moon was alarmed by the reports of continued violence and human rights violations in Syria, which resulted in an increased flow of refugees into neighbouring countries, his office said on Monday. The timeline for the complete cessation of violence endorsed by the Security Council must be respected by all without condition.
Failure to end the violence would turn attention back to the diplomatic stalemate that has left Western and Arab powers on the one hand and Assad's friends in Russia, China and Iran on the other all calling for calm. But they are sharply at odds over how that might be achieved and how Syria would be governed from then on.
For graphic on fighting http://link.reuters.com/zan47s
For Interactive timeline http://link.reuters.com/pyt37s
Syrian Foreign Minister Walid al-Moualem was in Moscow for talks on Tuesday with his Russian counterpart Sergei Lavrov. One of Lavrov's deputies said Russia was working with the Syrian authorities to promote talks with the opposition. But he reiterated Moscow's vocal opposition to foreign intervention.
There was also no sign the rebels were holding fire.
Opposition activists, denounced by Assad and his aides as foreign-backed terrorists, said their lightly armed and scattered forces had mounted fatal attacks on troops. They accused government forces of bombarding villages around Idlib in the northwest, as well as attacks elsewhere in the country of 22 million.
Among the forces ranged against Assad and hoping, with Western blessing, to end his family's four-decade rule there was more talk of war than of peace. One general who defected to the rebels demanded foreign air strikes on the artillery and tank units that are the spearhead of the Assad government's response to calls for change inspired by last year's Arab uprisings.
You will not need a long air campaign. Seventy percent of the Syrian military is already out of action and air strikes would be a message to the Syrian people that the international community is really with them, Mustafa al-Sheikh told Reuters at a camp where Turkey is giving refuge to Syrian army officers.
Saying Assad could not rely on conscript troops from the Sunni Muslim majority to follow orders from an officer corps dominated by members of the president's minority Alawite sect, the general urged the United States, Turkey and Arab states to mount the kind of strikes used against Yugoslavia in the 1990s. The aim would be to create safe areas for Syrian army deserters to gather.
Such talk among the fractious rebel movements, like calls from others for more weaponry to be smuggled in to opposition groups on the ground, has fallen on deaf ears.
Assad's Alawites, many of whom, even beyond the wealthy elite around the president's family, see themselves engaged in a battle for survival. They have lined up with Shi'ite Iran against an Arab world where Sunni Islamists are in the ascendant.
Russia and China share a concern that Western democracies have been pushing to expand the remit of the United Nations into interfering in member states in a way that threatens their own interests at home, adding vigour to their defence of Assad.
After dramatic internal changes wrought in Tunisia, Egypt and elsewhere last year by popular Arab uprisings, and the swift collapse of Muammar Gaddafi's rule in Libya with the help of Western air power, the conflict in Syria has the makings of a much longer, and bloodier, standoff.
For the time being the regime feels comfortable with the situation as it is. It wants more time to carry out its own approach to the popular challenge, in a military fashion, said Peter Harling, an analyst at the International Crisis Group, who saw little prospect of Assad complying rapidly with a truce.
Rather, he said, the Syrian authorities would continue to seek support from Russia - from whom it buys arms and provides a naval base on the Mediterranean - as well as Iran and China to face down fellow Arabs, Turkey and the West.
Rami Khouri, director of Issam Fares Institute at the American University of Beirut, said prospects for a truce this week had never been high: The battle lines are drawn.
Most of the Arab world, Turkey and the West have openly said they want to bring down the Syrian regime ... They will keep doing more and more things to bring that about.
It really becomes a question of how much the Russians and the Chinese can withstand being identified with this regime which is carrying out such terrible deeds against its own unarmed people, for the most part, Khouri said.
There is a point beyond which even the hard-nosed and hardball players like the Russians and the Chinese recoil.
(Additional reporting by Tulay Karadeniz and Jonathon Burch in Turkey, Louis Charbonneau and Michelle Nichols at the United Nations, Stephanie Nebehay in Geneva, Arshad Mohammed in Washington, Steve Gutterman in Moscow, and Douglas Hamilton, Mariam Karouny and Erika Solomon in Beirut; Writing by Alastair Macdonald; editing by Christopher Wilson)