The top U.S. military commander in Iraq, Army General Ray Odierno, said Tuesday that American combat forces have completed the planned withdrawal from Baghdad and other urban areas.

Speaking via satellite from Baghdad to reporters at the Pentagon, General Odierno said Iraqi security forces have taken control of all major metropolitan areas in the country.

"In accordance with the security agreement between the United States and Iraq, U.S. combat forces have completed the withdrawal out of Iraqi cities," he said. "A small number of U.S. forces will remain in cities to train, advise and coordinate with Iraqi security forces as well as enable them to move forward."

Odierno declined to estimate how many soldiers will remain in Iraqi cities, saying that number is likely to change on a day-to-day basis.

The general said that outside the urban areas, U.S. forces will continue to conduct operations in coordination with Iraqi forces.

"Our combined efforts will establish a layered defense." he said. "As Iraqis secure the cities, our combat forces, partnering with Iraqi security forces, will secure the belts and borders in an attempt to eliminate safe havens and sanctuaries and to limit freedom of movement of insurgents."

U.S. and Iraqi officials had warned that insurgent groups and militias were likely to step up attacks in the period leading up to the June 30 deadline. There have been several bombings, including one on Tuesday in Kirkuk that killed and wounded dozens of people.

General Odierno said some of the attacks are being carried out by militants with the help of neighboring Iran.

"We continue to still see training going on inside of Iran," he said. "We still believe weapons are moving and ammunition is moving from Iran into Iraq. We have not seen any adjustments made since the problem with the elections in Iran. They have kind of maintained themselves in a steady state."

Odierno said that when he first arrived in Iraq in 2006, the sectarian violence was so high it was difficult to see a way out.

The general noted that there has been a vast improvement in security since then that made the withdrawal possible.

"Today was just another sign that I have a lot of hope that Iraq is going to be able to move forward as a secure, stable, sovereign Iraq that could be a long-term partner with the United States in the Middle East who has a democratic government," he said.

General Odierno said there are about 131,000 U.S. troops in Iraq. He said he expects that number will be down to about 50,000 by September of next year. The U.S.-Iraq security agreement calls for the withdrawal of all U.S. forces by the end of 2011.