WASHINGTON - Gen. David Petraeus, in his first appearance in Washington since taking over as the top war commander in Afghanistan, is laying out a mostly upbeat assessment of military progress that should allow the United States to begin withdrawing forces this summer, despite predictions that the wounded Taliban insurgency will mount an especially bloody fight this spring.

No one is calling it the Taliban's last stand, but U.S. officials say this is the year that the insurgency will be tamed on the battlefield and at the bargaining table.

Petraeus met privately with Obama and Defence Secretary Robert Gates on Monday, the start of a full week of testimony and other events.

In a statement describing the meeting, the White House said the three discussed "the effectiveness of the military surge, the growth of the Afghan National Security Forces and President (Hamid) Karzai's expected March 21 announcement on beginning transition to Afghan security lead."

The optimism comes with some significant caveats, but it still marks a significant turn from worries a year ago about the strength and durability of the Taliban-led insurgency as the first of Obama's 30,000 additional troops worked to take and hold Taliban strongholds in southern Afghanistan.

Sen. John McCain of Arizona, the top Republican on the Armed Services Committee, said he expects Petraeus to "talk about the success they have had on the ground. Every observer who has gone over there has been impressed with that success." On the other hand, Petraeus will face tough questions from the committee about corruption in Karzai's government and the situation in Pakistan.

"I expect certainly some skepticism on both sides of the aisle," McCain said in an interview. "I don't see any kind of pressure to withdraw immediately."

Obama wants to begin reducing U.S. forces in Afghanistan in July with the aim of a full security transfer to the Afghans by the end of 2014 -- a goal the White House said Obama, Petraeus and Gates discussed on Monday.

Petraeus was expected to caution that the transition of control to Afghan security forces will be slow and difficult as the Kabul government struggles to find its footing. And commanders are planning for a brutal spring fighting season as insurgents try to regain their place and test the fledgling Afghan troops.

"There is no question that the injection of 30,000 additional American troops has had an impact on the Taliban's ability to operate," said Karl F. Inderfurth, a former senior State Department diplomat for South Asia. "The situation on the ground will almost certainly be the most promising part of the story that General Petraeus can tell."

Other difficult struggles will determine success, including the insurgents' safe havens in Pakistan, the reconciliation process with more moderate Taliban, and establishment of a more capable government, said Inderfurth, who is now with the Center for Strategic and International Studies.

He added that tensions over civilian casualties will hamper another critical element -- winning the hearts and minds of the Afghan people. Stability will only come when the people turn away from the Taliban, confront the insurgents and side with the U.S., its allies and the Afghan government.

Petraeus, who testifies to Congress Tuesday and Wednesday, is likely to repeat his claim that the troop surge has worked to oust the Taliban from historical strongholds, particularly in the south. And he will likely begin to sketch out how the gradual U.S. troop withdrawal can take place, with Afghan troops taking control in more stable locales as U.S. forces shift to still precarious regions.

A topic of continued debate will be the militants' safe havens along the mountainous Pakistan border, and Islamabad's reluctance to move into insurgent strongholds in North Waziristan -- where senior al-Qaida leaders including Osama bin Laden are rumoured to be hiding.

Members of Congress, meanwhile, will roll out a resolution calling for Obama to withdraw U.S. forces from Afghanistan either in 30 days or no later than Dec. 31, 2011. While the measure has failed in the past and is almost certain to fail again, the debate will underscore Congress' impatience with the war in the face of increasing budget pressure.

The lawmakers argue that the nation can't afford the war in times of deep budget cuts and a growing deficit. Lawmakers are eyeing the military's proposed budget of $553 billion for the next fiscal year as well as the $118 billion for war costs in Iraq and Afghanistan as potential budget-cutting prospects.

Opposition to the war remains high among Americans. A CBS poll in February asked if "the U.S. is doing the right thing by fighting the war in Afghanistan now, or should the U.S. not be involved in Afghanistan now." Fifty-four per cent said "not involved," while 37 per cent said the "right thing."

Petraeus carries a lot of weight with lawmakers who give him a good deal of credit for turning around the war in Iraq and beginning the withdrawal of combat forces there.

He was last in the Oval Office in June, when Obama fired Gen. Stanley McChrystal and turned to Petraeus as an emergency replacement. Petraeus left for Kabul immediately and has made a point of staying out of the political spotlight until now.

This week, Petraeus will argue for patience in an increasingly unpopular war, with his military reputation and war fighting legacy on the line. It may be the last time he testifies to Congress. Petraeus, 58, is expected to leave the Afghanistan job late this year, either to assume another top military post or to retire from the Army.