President Clinton's national security advisor, Sandy Berger, has given details of the United States' strategy on Iraq if United Nations weapons inspectors are not allowed back into the country.

In a speech in Washington, Mr Berger said the US was under an obligation to renew attacks on Iraq if President Saddam Hussein continued with his weapons programme.

He also said more attention would be paid to deepening co-operation with Iraqi opposition groups seeking to overthrow Mr Hussein.

Mr Berger said the help would be practical and effective but he warned against expecting quick results.

In a sign of continuing hostility, Iraq announced earlier that it had banned all UN civilian flights to and from the country.