PHOENIX (Reuters) - Republican John McCain on Tuesday questioned rival Barack Obama’s belief in American leadership in world affairs with two days to go before the Democratic senator accepts his party’s nomination for U.S. president.

U.S. Senator John McCain (R-AZ) is interviewed by talk show host Jay Leno (R) on "The Tonight Show with Jay Leno" at the NBC studios in Burbank,California August 25, 2008 in this publicity photograph released by NBC. REUTERS/Paul Drinkwater/NBC/Handout

McCain, 71, suggested Obama, 47, had failed to express confidence in America as “the greatest force for good on this earth” when he gave a speech in Berlin last month before more than 100,000 people.

“He was the picture of confidence. But in some ways confidence itself and confidence in one’s country are not the same,” McCain he told a group of American war veterans.

McCain and Obama are vying to succeed Republican President George W. Bush, who must step aside in January after eight years in office. McCain’s campaign insists it does not question Obama’s patriotism but merely his judgment.

Previous assertions by McCain that Obama cares more about political positions than issues of substance such as winning the Iraq war have angered the Democratic candidate, who has told his opponent not to question his patriotism.

McCain, himself a war veteran imprisoned for more than five years in Vietnam, accused Obama of appearing to link the U.S.-led invasion of Iraq in 2003 to Russian military action in Georgia in recent weeks.

Obama last week condemned Moscow’s actions in Georgia and said Russia could not “charge into other countries” but he also said: “Of course it helps if we are leading by example on that point.”

His remarks were widely seen as a criticism of the war in Iraq, which Obama opposed. McCain used the comments to raise broader questions about Obama, suggesting he lacked the clarity and vision to lead America and the world.

“If he really thinks that by liberating Iraq from a dangerous tyrant, America somehow set a bad example that invited Russia to invade a small, peaceful and democratic nation, then he should state it outright because that is a debate I welcome,” McCain declared.

“Confusion about such questions only invites more trouble, violence and aggression,” said McCain, who as a senator has specialized in defense and foreign affairs issues and has put national security at the center of his campaign.

He and Obama are running neck-and-neck in opinion polls.