Getty Images Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama speaks during the Veterans of Foreign Wars national convention in Orlando, Florida.

Addressing the Veterans of Foreign Wars convention, Obama reaffirmed his early opposition to the U.S. invasion of Iraq and said the so-called “surge” strategy of sending 30,000 additional troops to Iraq last year had not produced the political reconciliation necessary to achieve lasting peace in the country. McCain supported the Iraq invasion and was an early champion of the surge.

“These are the judgments I've made and the policies that we have to debate, because we do have differences in this election,” Obama said. “One of the things that we have to change in this country is the idea that people can't disagree without challenging each other's character and patriotism. I have never suggested that Sen. McCain picks his positions on national security based on politics or personal ambition. I have not suggested it because I believe that he genuinely wants to serve America's national interest. Now, it's time for him to acknowledge that I want to do the same.

Video Democratic presidential candidate Barack Obama is criticized Republican rival John McCain Tuesday at a VFW convention in Orlando, Florida; for questioning his patriotism and his judgment on national security matters, especially on Iraq. Media Player The FREE Windows Media Player is necessary to play Windows Media.

“Let me be clear: I will let no one question my love of this country,” Obama said to applause.

McCain stood before the same audience a day earlier and said Obama “tried to legislate failure” in the Iraq war and had put his ambition to be president above the interests of the United States. He said the Illinois senator did this by pushing for a timetable for withdrawal of U.S. combat troops from Iraq and by voting in the Senate against a major appropriations bill to help fund the troop increase.

A decorated Vietnam war veteran and member of the Senate Armed Services Committee, the Arizona senator has sharply questioned whether the 47-year old Obama has the experience and character necessary to serve as commander in chief.

McCain has also spoken out strongly against Russia's invasion of the Republic of Georgia, using Obama's absence from the campaign trail last week when he was on vacation in Hawaii to take a hard line against the Russian government. His tough talk led some of Obama's foreign policy advisers to suggest McCain may have complicated the conflict.

Obama strongly condemned Russia's actions Tuesday but said the U.S. involvement in Iraq had imperiled U.S. ability to take a leadership role in the matter.

“We failed to head off this conflict and lost leverage in our ability to contain it because our leaders have been distracted, our resources overstretched, and our alliances frayed,” Obama said.

The Illinois senator also praised Joseph Biden, the Senate Foreign Relations Committee chairman thought to be among the top contenders to be Obama's running mate, for calling for an additional $1 billion for reconstruction projects in Georgia.