President Barack Obama Monday renewed US sanctions on Syria for a year, accusing Damascus of supporting "terrorist" groups and pursuing missile programs and weapons of mass destruction.
There had been no expectation that Obama would lift the measures, but the renewal came at an especially sensitive time in often tense US-Syria relations, despite efforts by the administration to return an ambassador to Damascus.
Obama said in a message to Congress renewing the sanctions imposed by former US president George W. Bush in 2004, that the Syrian government had made "some progress" in suppressing the infiltration of foreign fighters bound for Iraq.
But he added that its "continuing support for terrorist organizations and pursuit of weapons of mass destruction and missile programs, continue to pose an unusual and extraordinary threat to the national security, foreign policy, and economy of the United States."
Obama also called on Syria to demonstrate "progress" in the areas that Washington says justify sanctions, to allow them to be lifted in future.
US Secretary of State Hillary Clinton last week warned Syrian President Bashar al-Assad against the risk of sparking a regional war if he supplies long-range Scud missiles to Hezbollah, a Shiite militia group.
"President Assad is making decisions that could mean war or peace for the region," she told a pro-Israel group.
But Syria has dismissed the accusations and warned Washington against taking Israel's claims seriously.
Some US lawmakers have seized upon the accusations to argue against any rapprochement between Washington and Damascus.
In February, Obama nominated career diplomat Robert Ford as the country's first ambassador to Syria in five years, but his appointment has yet to be confirmed by the Senate.
Bush declared a national emergency regarding Syria on May 11, 2004, and imposed economic sanctions over charges it was a state sponsor of terrorism. They were extended in 2006, tightened in 2007 and renewed the following year.
Monday's action marked the second renewal of the sanctions regime by Obama.
Ties between Washington and Damascus became badly strained after the US-led invasion of Iraq in 2003, and the assassination of Lebanese leader Rafiq Hariri in 2005, which was blamed on Syria.
Washington recalled its ambassador in February 2005 following Hariri's murder and it took five years before Ford was named.
Damascus has denied any involvement in Hariri's killing.