BAGHDAD—Prime Minister Nouri al-Maliki ruled out the presence of any U.S. troops in Iraq after the end of 2011, saying his new government and the country's security forces were capable of confronting any remaining threats to Iraq's security, sovereignty and unity.

A majority of Iraqis—and some Iraqi and U.S. officials—have assumed the U.S. troop presence would eventually be extended, especially after the long government limbo. But Mr. Maliki was eager to draw a line in his most definitive remarks on the subject. "The last American soldier will leave Iraq" as agreed, he said, speaking at his office in a leafy section of Baghdad's protected Green Zone. "This agreement is not subject to extension, not subject to alteration. It is sealed."

"For Iraq to be dragged into an axis or an orbit, that's impossible, and we reject it whether this comes from Iran, Turkey or the Arabs," he said.