Washington ? The Bush administration moved steadily Monday toward a military showdown with Iraq and suggested a decision could come as early as next week after U.N. inspectors credited Iraq with only limited cooperation in the search for weapons.

To bolster its case, the United States intends to provide the inspectors with additional evidence to support its claim that President Saddam Hussein has been moving and hiding thousands of chemical and biological weapons in palaces, mosques and private homes.

A senior Bush adviser, speaking on condition of anonymity, said Secretary of State Colin Powell would unveil next week “broad evidence” against Saddam, including new information about his ties to al-Qaida, his weapons of mass destruction program and his efforts to deceive the world community by hiding his deadly arsenal beneath the ground and in mobile facilities.

Some officials are expecting President Bush to have Powell deliver the material at the United Nations, but details were still being worked out Monday. The decision comes as Democrats and anxious U.S. allies intensified demands for proof that Saddam possesses weapons of mass destruction.

Bush and his senior advisers refused to tip their hand on when the United States might go to war to force Iraq to disarm.

But the Pentagon pushed ahead with war preparations that would position more than 150,000 troops and four aircraft carrier battle groups, each with more than 70 warplanes, in the Persian Gulf region by the end of February.

To facilitate the flow of war materiel to the Gulf, 13 more cargo ships from the Transportation Department’s Ready Reserve Force fleet have been activated, the department announced Monday. They join 19 other ships already activated.

The Ready Reserve Force ships are operated by American merchant mariners who volunteer for the missions. The fleet augments cargo ships of the Navy’s Military Sealift Command.