A deadline for Syria to accept a peace plan put together by the Arab League has passed, at the end of a day marked by more violent deaths.
Syria has agreed in principle to accept the peace plan, but critics accuse it of stalling for time.
In an interview with the UK's Sunday Times, President Bashar al-Assad was defiant, saying he would "not bow down" in the face of foreign pressure.
At least 24 people were killed in clashes on Saturday, said activists.
The UN says more than 3,500 people have died in Syria's repression of the pro-democracy uprising since March, while many others have disappeared or been jailed.
There has been mounting international pressure on Syria to end its crackdown. The Arab League has suspended Syria and given it an ultimatum to accept a plan to end the violence or face sanctions.
The deadline for Syria to accept the plan passed at 22:00 GMT on Saturday.
On Friday, Syria said in principle it would accept observers to monitor implementation of a peace deal, but with conditions.
The head of the Arab League said it was studying a letter from Syria seeking changes to its proposed observer mission. Reports say Damascus is seeking to reduce the observer delegation to 40 from 500.
The observers are supposed to oversee the implementation of the rest of the plan, which requires the government to stop attacking demonstrators, pull its military out of restive areas and begin negotiations with the opposition.
But in his interview with the Sunday Times, Mr Assad accused the Arab League of creating a pretext for Western intervention in his country, which he said would trigger an "earthquake" across the Middle East.
Mr Assad said his soldiers were under attack and the response was to "search for the armed people, chase the armed gangs, prevent the entry of arms and weapons from neighbouring countries, prevent sabotage and enforce law and order".
There were 24 more deaths on Saturday, according to the umbrella organisation covering the main opposition groups. The Local Co-ordination Committees said the toll included 10 in Homs, five in Qusair, nine in the town of Kafr Takharim in Idlib province, three in the town of Halfaya in Hama, and one each in Deraa and Bokamal.
The Qusair toll included two army defectors and two civilians killed in a clash with troops.
But the LCC tally did not appear to include four intelligence agents reportedly killed when defecting soldiers attacked their car in Homs.
The BBC's Jim Muir, in neighbouring Lebanon, says Syrian authorities face a dilemma: if they allow the situation to be stabilised with observers, and pull their troops out, they could see large parts of the country falling outside their control.
Syria is aware that Libya's suspension from the Arab League helped persuade the UN Security Council to authorise the military action which helped topple Col Muammar Gaddafi.
But the international community remains divided over Syria, with Russia urging restraint.
The US, while warning that the situation could escalate into a civil war, says there is little appetite in the international community to intervene in Syria.
British Foreign Secretary William Hague will meet members of the opposition Syrian National Council (SNC) and the National Co-ordination Committee for Democratic Change in London on Monday, his office said.