This is according to congressional officials and other sources familiar with the matter.
Though the White House insists no final decisions have been made, senior administration officials on Friday informed Florida Republican Representative Ileana Ros-Lehtinen, a senior member of the House International Relations Committee, that an announcement was "imminent".
Several sources said the administration was leaning towards imposing economic rather than diplomatic sanctions under legislation signed into law by President George Bush in December.
Washington accuses Syria of sponsoring "terrorism", occupying Lebanon and failing to secure its border with Iraq while allowing anti-American fighters to cross into the country.
"Damascus' destabilising behaviour in the Middle East has only gotten worse," US Representative Eliot Engel, a New York Democrat, said in urging Bush to act.
The administration's move against Syria would stand in stark contrast to Bush's decision to ease sanctions on Libya as a reward for scrapping its nuclear arms programmes.
Bush has seized on Libya's pledge to abandon weapons programmes as an example for other countries, including Syria.
The Syria Accountability Act bars trade in items that could be used in weapons programmes until the administration certifies Syria is not supporting terrorist groups, has withdrawn personnel from Lebanon, is not developing unconventional weapons and has secured its border with Iraq.
The law also authorises Bush to impose at least two other sanctions from a menu that includes barring US businesses from investing in Syria, restricting travel in the United States by Syrian diplomats, and banning exports of US products other than food and medicine to Syria.
Bush might bar US companies
from investing in Syria
The legislation allows the White House to waive the sanctions, but a senior administration official said: "We will implement the Syrian Accountability Act."
The official declined to say which sanctions would be put in place and when.
Several sources said the announcement was likely to be made next week or the week after.
The White House informed Ros-Lehtinen the announcement was imminent in response to her letter urging Bush to expedite implementation of the sanctions. The congresswoman heads a House of Representatives subcommittee on the Middle East.
"They're ready to go," another source said of the sanctions, calling it "a serious signal to the Syrians that it needs to throw out terrorist groups".
Syria says its support for the Palestinian and Lebanese groups it calls freedom fighters is merely political and their only activity in Syria is speaking to media.
Syria says its support for
freedom fighters is political
Allegations from Washington during the Iraq war that Damascus was helping aides of former Iraqi President Saddam Hussein flee raised concern in the Arab world Syria could be the next target of what the US calls its "war on terror".
US Defence Secretary Donald Rumsfeld complained last month Syria was not doing enough to stop guerrillas entering Iraq.
But with trade between the two countries a modest $300mn or less annually, the sanctions would have more political than economic effects.
Sources said they expected the administration to impose the sanctions gradually. These could include blocking transactions in which the government of Syria has any interest and reducing US diplomatic contacts with Syria.