US President George W Bush says war may be unavoidable if Iraq refuses to disarm.
Declaring Iraq as a "grave and growing" threat to the US, Mr Bush is seeking domestic support for a measure authorising the use of force if necessary to disarm Saddam Hussein.
But while US officials press on with their campaign for a tough new UN resolution on Iraq, Russia is insisting on a swift return of international weapons inspectors to Iraq under their existing mandate.
In his weekly radio address from his family's seaside compound at Kennebunkport, Mr Bush called Iraqi President Saddam Hussein "a cruel and dangerous man" who had deceived the world about his weapons of mass destruction for 11 years.
"Our country values life and we will never seek war unless it is essential to security and justice," Bush said, previewing a speech next week in which he will explain to the American people, the US Congress and the United Nations why the United States is prepared to go to war to disarm Baghdad.
"We hope that Iraq complies with the world's demands," Mr Bush said. "If, however, the Iraqi regime persists in its defiance, the use of force may become unavoidable. Delay, indecision and inaction are not options for America, because they could lead to massive and sudden horror."
Washington is working with Security Council members to win support for a new resolution on weapons inspections which would threaten military action if Iraq failed to comply with the council's demands.
Britain has backed the US text, but Russia, France and China have all expressed their opposition.
"There are no serious obstacles to inspectors returning to Iraq as soon as possible," Russian Foreign Minister Igor Ivanov told Russian television. "From a legal point of view, no new UN Security Council resolution is required for the return of inspectors."
"Russia thinks that right now the most important thing is that the inspectors return to Iraq as soon as possible and start their work," Mr Ivanov said, adding that October 19th had been named as the date for a first group of inspectors to fly out.
Mr Bush will devote a rare, televised evening address on Monday to arguing his case against Saddam and outlining the threat he believes is posed by Baghdad's alleged chemical, biological and nuclear weapons programmes.