The United Nations Security Council has postponed until Thursday a vote on a Western-backed resolution that threatens Syrian authorities with sanctions in a bid to end the 16-month conflict.
Russia's UN envoy said further talks on the measure will be held today.
International envoy Kofi Annan had requested the delay amid differences between Moscow and the resolution's Western sponsors over whether Damascus should be threatened with sanctions.
Earlier, Syrian President Bashar al-Assad's brother-in-law Assef Shawkat and Syria's defence minister were killed in a bomb attack at a national security building in Damascus.
British Foreign Secretary William Hague condemned the suicide attack, and said it "confirms the urgent need for a Chapter 7 resolution of the UN Security Council on Syria".
German Chancellor Angela Merkel said the bombing "shows us that it is high time to ratify the next UN resolution."
Chapter 7 allows the 15-member council to authorise actions ranging from diplomatic and economic sanctions to military intervention.
US officials have said they are talking about sanctions on Syria, not military intervention.
The White House said President Assad was losing control of Syria and the US was working urgently with international partners to push for a political transition.
Spokesman Tommy Vietor said there was real momentum against Mr Assad and it is "time for the Syrian people and the international community to focus on what comes next".
French Foreign Minister Laurent Fabius said Paris would also push for the resolution.
The UN has until Friday to renew the mandate for observers in Syria.
Western nations want China and Russia to back tougher measures to stop the fighting.
UN Secretary-General Ban Ki-moon has arrived in Beijing, where he called for rapid unified action by the Security Council to tackle the crisis.
Analysts said the bomb attack will weaken morale and might accelerate high-level defections, but does not signal the president's imminent downfall.
Gala Riani, a Middle East analyst at the Control Risks consultancy, said the suicide bombing was "in some ways the most successful direct attack on the regime we've had so far.
"At the very least, we can expect the situation to continue to deteriorate. But I think it will take more than this to take the Assad regime down."
Anthony Skinner, head of Middle East consultancy Maplecroft, said the attack will send "a stark message that individual ministers are not safe and is likely to accelerate the erosion of the regime's support base".
The bombing, claimed by the Free Syrian Army and also by Islamist group Liwa al-Islam, does not alter the fact that the rebels remain hugely outgunned by President Assad's forces.
"These are very significant developments, but I believe the offensive will be repelled," Mr Skinner said. "Psychologically, though, this will likely give the FSA a significant boost and may also precipitate more defections at a senior level."
Fighting has reportedly intensified across Damascus, where activists say the military has deployed tanks and helicopters.
Shooting was reported in one of the main central streets and a square housing the Central Bank.
Rebel forces say the military has launched an all-out assault on the capital, calling it Operation Damascus Volcano.
Reports from Syria cannot be independently verified as the government has barred international journalists and rights groups.
