US President George W Bush has ordered expanded economic sanctions against senior Syrian officials and their associates, the White House has said.
The US accuses Syria of sponsoring and harbouring terrorists
The US assets will be frozen of those responsible for actions that "undermine efforts to stabilise Iraq" or to have benefited from public corruption.
Mr Bush also reasserted US allegations that Syria was seeking to undermine democracy in neighbouring Lebanon.
Damascus has repeatedly denied the claims by Washington.
Mr Bush announced his decision in an executive order and a message to the US Congress. He did not state which officials would be affected.
Washington previously imposed economic sanctions on Syria in 2004 mainly for its support of Lebanese opposition group Hezbollah and Palestinian militant group Hamas.
It has since blacklisted several Syrian officials.
In 2005, Syria withdrew its troops from Lebanon after a presence of 29 years, after massive domestic and international pressure following the assassination of the former Lebanese premier, Rafik Hariri.
However, the US says Syria has continued to interfere in Lebanon.
"Syria continues to undermine Lebanon's sovereignty and democracy, imprison democracy activists, curtail human rights, and sponsor and harbour terrorists," the White House said.
The statement also asserted that Syria was undermining efforts to stabilise Iraq and allowing Syrian territory to be used for that purpose.
Syria's government "continues to pursue other activities that deny the Syrian people the political freedoms and economic prosperity they deserve, and that undercut the peace and stability of the region," it said.