President George Bush had planned earlier this week to curb future investments by American energy firms in Syria and prohibit Syrian aircraft from flying into the United States.
Bush was also expected either to block transactions involving the Syrian government or ban exports to Syria of US products other than food and medicine.
But a congressional source on Thursday said the decisions have been put on hold for the time being.
"The situation on the ground in the Middle East warrants that the announcement be postponed," he said.
"The situation on the ground in the Middle East warrants that the announcement be postponed"
Sources said the sanctions were now likely to be delayed until mid-April, underscoring US and international concerns their imposition could exacerbate tensions in the region following the assassination of Hamas leader Shaikh Ahmad Yasin.
Administration officials said Bush was not backing away from the sanctions, under legislation he signed into law in December known as the Syria Accountability Act. They said the decision to impose them had been made, but the timing was in flux.
Washington has been at loggerheads with Syria, accusing it of aiding "terrorists" and aiding anti-Israel fighters.
Syria denies giving more than political support to those fighting the Israeli occupation.