"We urge the Syrian government to step up and start fighting the war on terror in a more significant way by shuttering the offices of terrorist organisations who are headquartered or have facilities in Damascus," White House spokesman Tony Snow told reporters.
Mr Snow did not specify any organisations.
It’s the second day that Mr Snow only had measured praise for Syrian law enforcement officials who thwarted a daylight attack on the US embassy in Damascus, saying they "did their job professionally."
Syria has also earned rare praise from the US Secretary of State Condoleezza Rice, “I do think that the Syrians reacted to this attack in a way that helped to secure our people and we very much appreciate that.”
Improved relationship
Syria has suggested that its efforts in stopping the attack, in which Islamist gunmen using mortars, automatic weapons and explosives-rigged vehicles attempted to storm the US compound, could pave the way for an improvement in tense relations between the two countries.
"The ball is now in the US administration's court," Syria's ambassador to Washington, Imad Mustafa, told the official Ath-Thawra newspaper.
"The policies followed by this administration do not help in improving relations in a positive fashion," Mr Mustafa said. "There is a chance to improve these relations because Syria has always believed in dialogue as a means to solving all problems and pending issues."
Three attackers and one Syrian security guard were killed in the resulting gun-battle outside the embassy following the unprecedented attack which also left 14 people injured, but no American casualties.
So far, no group has claimed responsibility for the attack.
The US embassy in Syria remained closed on Wednesday amid warnings to Americans to keep a low-profile in the country.
Relations between the United States and Syria took a turn for the worse in February last year amid accusations that Syria was involved in the murder of former Lebanese Prime Minister Rafiq Hariri.
Tensions have also mounted over Syria's support for the Lebanese Muslim Shi’ite group Hezbollah, just last week the White House branded Syria and regional ally Iran "especially worrisome" threats.