On a surprise visit to Iraq, Saturday, U.S. Secretary of Defense Robert Gates told US troops that their mission in Iraq was in its "end game" while adding that the United States intends to boost its presence in Afghanistan.

U.S. Defense Secretary Robert Gates addressed American troops in Balad, Iraq, Saturday, telling them that the United States is now in the "end game" in Iraq, while insisting that their contribution to stability remains of vital importance, in tandem with the recent decision that the United States will boost its military presence in Afghanistan.

In a town hall meeting with U.S. military personnel, Gates detailed President-elect Barack Obama's vision for a proposed drawdown, explaining that it represents a "significant change of mission."

Mr. Obama has vowed to withdraw U.S. forces from Iraq in 16 months and the recently signed military pact with Iraq calls for a U.S. withdrawal by 2011.

Gates calculated broadly that U.S. troops will be "out of cities and populated areas" by June 30. That date precedes a planned Iraqi referendum on the security pact in July.

"That's the point at which we will have turned over all 18 provinces to provincial Iraqi control," he said, adding that Iraqi forces will gradually shoulder more and more of the burden of security.

"Our forces will draw down over time and become less visible," said Gates. "Iraqi security forces will continue to shoulder more and more of the burden every day. But despite what you might hear about an increased focus on Afghanistan, let there be no doubt that your mission and the mission of all American troops in Iraq remains incredibly important during this crucial transition period."

However, top US Commander in Iraq, General Raymond Odierno said on Saturday that some US forces would remain remain at local security stations, as training and mentoring teams despite the summer deadline to pull American combat troops from urban areas.

Gates' visit to Iraq comes just over two weeks after the Iraqi parliament voted to ratify a new security pact with the United States, due to go into effect on January 1.

Some experts question whether the Iraqis are prepared to take over security and will they be ready when US troops withdraw from urban areas. Iraqi Defense Ministry Spokesman Mohammed al-Askari, however, insists that Iraqi forces are "ready to take control or we wouldn't have signed the agreement."

Urgent requests from commanders in Afghanistan to send more troops have added to the pressure to cut troops in Iraq.

But on Saturday Gates tried to reassure US troops in Iraq that despite a recent focus on the US presence in Afghanistan, the U..S mission in Iraq remained "incredibly important."

Military leaders have said repeatedly they cannot send the desired 20,000 or more forces to Afghanistan unless troop levels are reduced in Iraq. Gates, nevertheless, insisted that the US military presence in Afghanistan would never reach the same scope as that in Iraq.

"It's highly unlikely that we will ever have a troop presence in Afghanistan anything like we have had in Iraq," he said. "And so I think we will meet General [David] McKiernan's request for the four additional BCTs [Brigade Combat Teams] over the course of the next year or so, but as I've said on this trip; I would be very concerned about a substantially bigger US presence than that in Afghanistan."

"The Soviets were there with 120,000 troops and lost because they didn't have the support of Afghan people and at a certain point we get such a big footprint we begin to look like an occupier and not an ally or supporter of the Afghans," he added.

Gates said he would be "very concerned" about a substantially larger US presence than the four brigade combat teams that General David McKiernan, commander of US and NATO troops in Afghanistan had requested.

The U.S. defense secretary's comments on Afghanistan come just days after the United States said it will pour thousands more troops into Afghanistan by next summer.   Gates announced from Kandahar on Thursday that the military can expect to commit a sustained force in Afghanistan for several more years.