The White House says the bomb attack which killed at least three top members of Syrian President Bashar al-Assad's regime shows Assad is "losing control."
Defense Minister Daoud Rajha, Deputy Defense Minister Assef Shawkat -- Assad's brother-in-law -- and General Hassan Turkmani, head of the regime's crisis team, died in the July 18 blast, according to state-run media.
Interior Minister Ibrahim al-Shaar was reported seriously injured.
In a statement, the White House also called on the international community to unite around a plan to transition Assad from power.
UN chief Ban Ki-moon said he "strongly condemns" the attack. Ban and Kofi Annan, the UN-Arab League envoy, called on the UN Security Council to take strong action on Syria ahead of a July 19 vote on a Western-backed resolution calling for harsh sanctions.
The vote, initially planned for July 18, was postponed for one day because of the bombing.
Ban said there was an "extreme urgency" for action to make government and opposition forces halt the violence. Annan said the council must take "decisive" action on the conflict.
Russia and China are expected to veto the resolution.
U.S.-Russia Phone Call
The White House also said that U.S. President Barack Obama had called Russian President Vladimir Putin to discuss the situation.
Foreign Minister Sergei Lavrov on July 18, however, reiterated Russia's opposition to the UN resolution, saying international sanctions would amount to “outright support of a revolutionary movement.”
In Damascus, security forces loyal to Assad flooded the streets after the attack, and snipers took up positions on rooftops.
However, spontaneous public celebrations broke out following reports on Syrian TV of the bomb attack, in spite of days of fierce fighting around the capital.
The rebel Free Syrian Army (FSA) claimed responsibility for the blast, but so did an Islamist rebel group named Liwa Al-Islam, or “The Brigade of Islam."
Syria's rebel commander, Riad al-Asaad, said from Turkey that his forces had planted the bomb inside the meeting room.
Radwan Ziadeh, the foreign relations officer of the opposition Syrian National Council, told Reuters from Washington the attack marks the beginning of the end for Assad's regime.
"This will be tipping point. Because the Assad regime will know that he is, he will be fighting till the end," Ziadieh said.
On July 18 the United States also imposed sanctions on an additional 29 Syrian officials and six Syrian companies, expanding its growing blacklist.
Based on reporting by AP, AFP, dpa, and Reuters