In a speech in Washington, Mr Berger said that the United States would attack Iraq again if it sought to redevelop weapons of mass destruction.

The speech was part of an effort by the US to lay out a strategy for containing Iraq if, as seems likely, the United Nations weapons inspectors are not allowed back in.

It went on to lay down limits to US support for efforts to overthrow Saddam Hussein.

Warning to Iraq

Mr Berger repeated the American position that there would be further air attacks if Iraq's weapons programme continued.

Sandy Berger: No quick results

The United States, he said, had the obligation, the will and the forces to do this.

As for working to topple the Iraqi leader - now an aim of American policy - Mr Berger offered help to the Iraqi opposition but warned against expecting quick results.

Help would be given in a practical and effective way, step by step. He said the United States would not play recklessly with lives and would not offer commitments before it was clear about risks and benefits.