US B-52 bombers carrying cruise missiles took off from Guam heading for Iraq early this morning for possible strikes in retaliation for the Iraqi incursion into its Kurdish dominated north.
Pentagon sources said a limited strike was likely.
The deployment of the strike force - which US government sources said might be directed at a single target - came after Washington claimed that Iraqi troops were moving deeper into Kurdish opposition held territory.
The decision to respond to Iraqi President Saddam Hussein's latest military manoeuvres was made by President Clinton as he campaigned for re election in Milwaukee, Wisconsin.
White House spokesman Mike McCurry said the president had decided on a response to "Iraq's aggression" but declined to say what it was. NBC news, however, reported that the United States would target Iraqi command and control installations.
Asked when any action would take place, Mr McCurry said: "I don't think the president is going to be saying anything in the middle of the night . . . I plan to go home and get a good night's sleep."
According to Washington, the Iraqi military advance threatened the town of Sulaymaniyah, the administrative capital of the Kurdish opposition.
"There was, you know, some discussions about redeploying his units outside the town of Arbil," Mr McCurry said. "Some of that did happen although they remained in firm control of the area. There is other evidence that he (Saddam Hussein) is using some of that force to penetrate deeper into Kurdish occupied territories in northern Iraq".
McCurry said there was also "reason to believe" that some Iraqi troops were involved in executions of leaders of an antiBaghdad Kurdish faction in Arbil.
Mr Clinton, who placed US forces in the Gulf region on high alert on Saturday when the crisis blossomed, had defined "a course of action and has been consulting some governments and informing some governments of that course of action," Mr McCurry said adding "political, diplomatic, economic measures (or) any combination of those things could be included in an appropriate response".
President Clinton made no mention of the crisis in his Labour Day speeches but, after addressing a crowd of about 25,000 in Green Bay, Wisconsin, he went to his temporary headquarters and telephoned French President Jacques Chirac.
"It was a useful, productive and candidate discussion of the situation in northern Iraq," Mr McCurry said. The president also conferred twice by telephone with White House chief of staff Leon Panetta and National Security Adviser Tony Lake, who were both back in Washington following the fast breaking situation.
The White House believes Saddam sent three tank divisions composed of 30,000-40,000 elite Republican Guard troops into northern Iraq to help a Kurdish faction involved in a bloody power struggle with another Kurdish group with links to Iran.
It claims UN Security Council resolutions approved after the 1991 Gulf War provide the legal basis for responding to Saddam's actions although this is disputed by some diplomatic sources. "Our interest is in keeping Saddam Hussein from believing that unjustifiable behaviour of this nature is cost free," Mr McCurry said.
He added that every time Saddam "has miscalculated and believed that he could use his military power with impunity, the international community has reminded him that he has obligations in the aftermath of his defeat in the Persian Gulf War".
Meanwhile, Mr Bob Dole, Mr Clinton's Republican presidential opponent, has raised the Iraqi issue in his campaign, saying on Sunday that the Clinton administration had brought on the crisis by failing to warn adequately against renewed aggression against the Kurds.
"Saddam Hussein has been testing American leadership and found it lacking," Mr Dole said.