U.S. Defense Secretary Donald Rumsfeld says the United States faces a "test of wills" with insurgents in Iraq.

During a previously unannounced visit, Mr. Rumsfeld Sunday met with Marines fighting in Al Anbar province, where the U.S. military said one American soldier was killed on Saturday.

Mr. Rumsfeld told the Marines that extremists in Iraq are fighting U.S. morale and struggling to control the perceptions of the conflict.

The secretary said he did not expect U.S. troop levels could be reduced before January, but said he hoped the American troops would eventually be relieved by newly trained Iraqi security forces.

Mr. Rumsfeld later flew to Baghdad to meet with senior U.S. and Iraqi leaders, including interim Prime Minister Iyad Allawi.