CHICAGO - U.S. President Barack Obama said in an interview with The Associated Press on Friday that he is confident the promised start of an American withdrawal from Afghanistan this summer will be significant and "not just a token gesture."

Obama also acknowledged that there exists a stalemate between Libyan rebel forces and Moammar Gadhafi, but he said he was very satisfied with the NATO air mission. The "noose is tightening" around the Libyan strongman, Obama said.

On the U.S. military prison at Guantanamo Bay, Cuba, the president said: "I still believe it should be closed."

He also voiced displeasure with legislation that forced his Justice Department to try Khalid Sheikh Mohammed, professed mastermind of the Sept. 11, 2001, attacks on the United States, before a military commission at the Cuban prison camp.

"I remain convinced we could have handled this in New York," Obama said. Attorney General Eric Holder had planned originally to try Mohammed in U.S. Federal Court in New York, but Congress intervened and made it illegal to bring suspected terrorist prisoners into the United States.

Obama was in Chicago to kick off his re-election campaign at a series of fundraising events in his adopted hometown. Asked about his greatest weakness as he prepares to face voters again in 2012, the president said he was most concerned about the economy because "there's still a lot of people unemployed ... people are still feeling being pressed."

As the election season begins, the United States is embroiled in a fight between Obama's Democrats and Republicans over best way to cut spending and put a cap on the country's skyrocketing budget deficit and alarming debt.

With the fight in progress over the 2012 budget, Obama said the contest of ideas would serve as a prelude to the coming need for legislators to vote on increasing the country's $14.3 trillion debt limit, a threshold that the Treasury says will be crossed within a few months. During the past decade the debt limit has been increased as a matter of routine.

With the election of a new crop of ultraconservative tea party-allied Republicans to the House of Representatives, however, they have threatened to vote against raising the limit. Members of the movement insist that government spending be cut and that it intrude less into the lives of U.S. citizens.

That, Obama said, "could plunge the world economy back into recession."

He conceded, however, that the borrowing limit would not be passed in the Republican-controlled House of Representatives unless it includes provisions to cut government spending.

"He's absolutely right it's not going to happen without some spending cuts," Obama said about warnings by House Speaker John Boehner.

The president said he welcomed the debate over how the U.S. spends its resources in the future, resources that he said must be increased by raising taxes on the upper income Americans, couples making more than $250,000 a year.

He said that to adopt the 2012 spending plan outlined by House Budget Committee chairman Rep. Paul Ryan would produce a "fundamentally different society than we have now."

Obama said Ryan's proposed changes to Medicare and Medicaid are "not compelled by the numbers" but rather by Republicans' desires "to give more tax breaks" to high income Americans. Medicare is the federal program that pays the medical bills of Americans 65 and older. Medicaid goes to the poor and disabled. Ryan and the Republicans want to change Medicare into a voucher program for that would be given to those now currently under age 55 when they reach retirement age. Critics say the vouchers would increasingly lose value as medical costs climb. The Medicaid program would see the federal government step aside from its administration, with block grants given to the 50 states for governors to administer.

Ryan also wants to cut tax rates for the wealthy to make them level with lower-income Americans and to remove loopholes.

Facing a need to find a middle ground, Obama said he did not "expect the Republicans to give in so I get 100 per cent of what I want," nor, he said, was he prepared to cede too much ideological ground to the opposition party.

Needed, he said, was "a smart compromise that's serious."

Looking toward the coming election campaign and continued weakness in the American economy, Obama said he must convince a nation suffering from stubbornly high unemployment that he deserves more time to help the economy recover from a recession he inherited from George W. Bush.

"I think the economy's going to continue to improve, and I think that I can make an effective case ... that not only have I been able to yank this economy out of that hole" but also that he has been able to start making wise fundamental changes. He pointed to overhauling the health care system, investing in clean energy and making college more affordable.

"I'm the person who is best prepared for us to finish the job so that we're on track to succeed in the 21st century," Obama said.

Looking overseas, Obama refused to say how many America troops would be involved in the July start of force reductions in Afghanistan. That decision, he said, awaited recommendations from top commander Gen. David Petraeus.

"I'm confident that the withdrawal will be significant," he said, "a real process of transition" and "not a token gesture."

On Libya, Obama said he does not anticipate any stepped-up U.S. military role, even as he conceded that a stalemate exists on the ground. He credited the United States and NATO with averting a "wholesale slaughter" of civilians and said Libyan leader Moammar Gadhafi is under increasing pressure leave Libya.

The president said Gadhafi is "getting squeezed in all different kinds of ways," running out of money and supplies.