Barack Obama restated his pledge to end the Iraq war by the summer of 2010, arguing that the U.S. must focus on defeating Al Qaeda in Afghanistan and keeping nuclear weapons out of the hands of Iran.

The presumptive Democratic presidential nominee, in a speech delivered ahead of a trip to the Middle East, said Tuesday in Washington, D.C., that the United States is still at risk of a terrorist attack, but the Iraq war has become a burden on the country that only diminishes security.

"This war distracts us from every threat that we face and so many opportunities we could seize," Obama said. "By any measure, our single-minded and open-ended focus on Iraq is not a sound strategy for keeping America safe."

Obama stressed several opportunities he said were lost as a result of the war, and reiterated that he will give the military a new mission if he is elected president: "ending this war."

John McCain, during a town hall meeting held just minutes after Obama delivered his address, said he knows "how to win wars" and that the strategy of increasing troop levels in Iraq should also be applied to Afghanistan.

"Senator Obama will tell you we can't win in Afghanistan without losing in Iraq. In fact, he has it exactly backwards," McCain said in Albuquerque, N.M. "It is precisely the success of the surge in Iraq that shows us the way to succeed in Afghanistan."

McCain also criticized Obama for laying out an Iraq policy without having visited both Iraq and Afghanistan.

"Senator Obama is departing soon on a trip abroad that will include a fact-finding mission to Iraq and Afghanistan," McCain said.

"He is speaking today about his plans for Iraq and Afghanistan before he's even left, before he has talked to General Petraeus, before he has seen the progress in Iraq, and before he has set foot in Afghanistan for the first time. In my experience ... fact-finding missions usually work best the other way around: First you assess the facts on the ground, then you present a new strategy."

McCain said as president he would track down Usama bin Laden and bring him to justice.

Obama went after McCain Tuesday for using the success of the troop surge to argue that Obama should change his pledge to end the war.

"But this argument misconstrues what is necessary to succeed in Iraq, and stubbornly ignores the facts of the broader strategic picture that we face," Obama said.

He said U.S. troops have "performed brilliantly" in lowering violence in Iraq, but that the surge brought other strains: on the military, on taxpayers and on security in Afghanistan.

Obama said he'd add at least two additional combat brigades in Afghanistan and exert pressure on Pakistan to step up the fight against Al Qaeda and the Taliban.

And he said he would couple aggressive and direct diplomacy with the threat of sanctions to keep nuclear weapons out of the hands of the Iranian regime.

At the top of his address, Obama repeated his pledge to end the war within 16 months of taking office.

Reserving the right to make" tactical adjustments" as the strategy is implemented, Obama said, "We can safely redeploy our combat brigades at a pace that would remove them in 16 months -- that would be the summer of 2010."

Obama was answering questions about his Iraq policy that arose after he said two weeks ago he may "refine" his strategy after visiting Iraq and Afghanistan. That was widely taken to mean he was considering adjusting his oft-stated plan to withdraw combat brigades within 16 months of taking office. Obama said at the time he was not talking about his withdrawal timetable.

Obama said Tuesday, though, he has been consistent in saying he would "consult with commanders on the ground and the Iraq government" in carrying out his strategy.

Obama said his five-point strategy also includes achieving energy security and "rebuilding our alliances."

"George Bush and John McCain don't have a strategy for success in Iraq -- they have a strategy for staying in Iraq," Obama said.

Meanwhile, the New York Daily News reported that the Obama campaign altered its Web site to remove a statement that Bush's surge of troops in Iraq "is not working." Over the weekend, the site was changed to describe an "improved security situation" at the cost of U.S. lives.

Campaign aide Wendy Morigi told the newspaper that Obama is "not softening his criticism of the surge. We regularly update the Web site to reflect changes in current events."

The Associated Press contributed to this report.