The top U.S. general in Iraq said Tuesday that he disagrees with a colonel's memo urging an early troop withdrawal although the security situation is better than expected since American forces turned over security in urban centers to the Iraqis more than a month ago.

Gen. Ray Odierno, the first senior American official to comment on the memo, told The Associated Press American troops need to stay the course in Iraq.

The Iraqi security forces face corruption and other problems but "overall it's gone very, very well," he said. But, he added, the Americans are still needed to protect security gains.

"Our goal here given us by the president is a secure, stable sovereign self-reliant Iraq. We're not there yet," he said in an interview at a U.S. base after meeting with Iraqi officials in the Anbar provincial capital of Ramadi.

Col. Timothy R. Reese, a U.S. Army adviser to the Iraqi military in Baghdad, wrote in his memo that the years-long American effort to train, equip and advise Iraqi security forces has reached a point of rapidly diminishing returns and the U.S. should go home next year, 16 months ahead of schedule.

Reese also wrote that Iraqi forces already are good enough to defend the government against the weakened terrorist and insurgent forces that remain active.

Odierno warned the security gains are fragile, saying the No. 1 threat was Kurdish-Arab tensions that could stoke violence in northern Iraq.

The Americans have pinned their hopes on national parliamentary elections scheduled for January to give the national reconciliation process a jumpstart by empowering disaffected groups.

Odierno said that would be the next benchmark.

"What we have to be able to do is to make sure that we reduce tensions so that they can solve this politically," he said. "It's important that we're here to make sure that we have legitimate credible parliamentary elections."

Reese argued for ending the U.S. military mission in Iraq in August 2010. That is the date when Obama has said all combat troops will have withdrawn, leaving behind a residual force of 35,000-50,000 troops to train and advise the Iraqi security forces until a final pullout by the end of 2011.

There are now 130,000 U.S. forces in Iraq.

"We want to continue to build the institutional capacity of Iraq to move it towards a stable country and we want to make them a long-term partner that would help us to, in my mind, help overall with the security situation in the Middle East. That's what our goals are," Odierno said.