The United States reiterated on Wednesday its call for Syria to close down the offices of any " terrorist organizations" operating in Damascus.

"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 organizations who are headquartered or have facilities in Damascus," White House spokesman Tony Snow said at a news briefing.

Washington has been accusing Syria of backing international terrorism, and demanding the Middle East country to "be an ally in fighting terror."

However, the White House praised for the second day Syrian security agents for repelling a terror attack on American Embassy in Damascus on Tuesday. Syrian law enforcement officials "did their job professionally," Snow said.

On Tuesday, four armed Islamic militants attempted to storm the U.S. embassy in Damascus using automatic rifles, hand grenades and at least one van rigged with explosives, the Syrian government said. All the assailants were killed in the attack, and no Americans were hurt.

U.S.-Syrian relations have been tense for many years with the two countries split on many issues, including Syria's role in Lebanon, the Middle East conflict and Iraq, and its support of militant groups in the region.

Washington recalled its ambassador to Syria following the assassination of former Lebanese premier Rafik Hariri, blaming Damascus for the murder. But Syria denied any role in the killing.

Source: Xinhua