Democratic presidential contender Barack Obama Wednesday called for the withdrawal of all U.S. combat troops from Iraq by the end of next year. Senator Obama unveiled his new plan for Iraq in a campaign speech in the early presidential contest state of Iowa. VOA national correspondent Jim Malone reports from Washington.

Obama said there is no military solution in Iraq and added that the best way to pressure Iraqi leaders into political reconciliation is to begin immediately removing U.S. troops.

Obama proposed drawing down one to two U.S. combat brigades each month until all combat troops are withdrawn from Iraq by the end of 2008.

"The best way to protect our security and to pressure Iraq's leaders to resolve their civil war is to immediately begin to remove our combat troops," said Obama. "Not in six months or one year, but now."

Obama also advocated an aggressive diplomatic effort involving Iraq's neighbors and the United Nations to help stabilize the country once U.S. troops are gone.

Obama reminded his audience that he opposed the Iraq war from the beginning, once again drawing a contrast with the frontrunner for the Democratic Party's presidential nomination, Senator Hillary Clinton of New York.

Clinton initially supported the war but now opposes President Bush's strategy on Iraq.

Obama trails Clinton among Democrats in the newest CNN poll by a margin of 39 to 20 percent, and in the latest Gallup survey by a margin of 48 to 25 percent.

Obama's proposal came after two days of congressional testimony from the top two Bush administration officials in Iraq, Ambassador Ryan Crocker and U.S. military commander General David Petraeus.

Both men said the security situation in Iraq has improved with the U.S. troop surge, but that Iraqi leaders need more time to bring about political reconciliation.

Crocker repeated that message to reporters at a Washington news conference Wednesday.

"This is going to take time," said Crocker. "It is going to take a lot of effort. It is going to take enormous resolve on the part of Iraqis and on the part of Americans to get this done."

President Bush will give a nationwide address Thursday on Iraq and is expected to endorse General Petraeus' recommendation for a gradual drawdown of 30,000 U.S. troops from Iraq by the middle of next year.

Democratic congressional leaders said that would not go far enough and described the Petraeus recommendation as unacceptable.