U.S. Secretary of Defense Robert Gates said Tuesday the Afghan war is a "greatest military challenge" for the United States and warned about "potential setbacks" in Iraq.

Gates made the remarks when giving lawmakers an early glimpse on President Barack Obama's war plans for Afghanistan and Iraq on the Capitol Hill.

While saying that there is no "purely military solution" for Afghanistan, Gates noted that more troops are needed "to provide a baseline level of security in some of the most dangerous areas."

The Pentagon is considering adding troops to Afghanistan in conjunction with "a dramatic increase in the size of the Afghan security forces," he added.

Gates is shedding some lights on how President Barack Obama plans to implement his campaign pledge to increase the U.S. focus on Afghanistan, where U.S. and NATO troops are battling a resurgent Taliban foe.

The Obama administration is conducting a full review of Afghan strategy, drawing on assessments by the military and former President George W. Bush's advisers.

U.S. military planners are working on a plan that could send 30,000 more U.S. troops to Afghanistan this year.

The exact number remains to be determined, as well as when they will arrive and what their specific missions will be.

Also to be defined is how to fulfill a pledge to increase diplomatic and economic resources.

Gates said the fight in Afghanistan will be "long and difficult," but the United States "can attain what I believe should be among our strategic objectives: an Afghan people who do not provide a safe haven for al Qaida, reject the rule of the Taliban, and support the legitimate government that they elected and in which they have a stake."

On Iraq, he said there is still the potential for setbacks. "There may be hard days ahead for our troops," he said.

The two wars in Iraq and Afghanistan are closely linked because the pace of the troop buildup in Afghanistan is partly dependent on how quickly the Obama administration draws down U.S. forces in Iraq.

Obama had promised to withdraw all combat troops from Iraq within 16 months after his swearing-in during his presidential campaign.

That will mean a quicker withdrawal than the plan written in an agreement signed by the former Bush administration and the Iraq government last year, which says the United States will pull out all troops from Iraq by Dec. 31, 2011.

However, Obama changed tone recently, saying he will seek to end the war in Iraq in a "responsible way."

Pentagon planners and U.S. military commanders have expressed fears that too rapid a pullout would jeopardize hard-won security gains.

Besides the wars, Gates also told lawmakers he faces tough choices on weapons spending that may lead to cuts in some programs.

He is testifying as Obama and the Congress are bargaining over tough budget issues generated by a skyrocketing federal deficit and the need to finance two wars and buy new weaponry.

(Xinhua News Agency January 28, 2009)