At the same time, he said the journey to two war zones, the Mideast and Europe was important because "many of the issues that we face at home are not going to be solved as effectively unless we have strong partners abroad."
Republicans have criticized Obama throughout his trip, and McCain's campaign said recently the Democrat was taking a "premature victory lap" with more than 100 days remaining in the presidential campaign.
In Arizona on Saturday, McCain took a swipe at the headline-making trip in a radio address on Iraq and energy that his campaign made available to the media: "With all the breathless coverage from abroad, and with Sen. Obama now addressing his speeches to the people of the world, I'm starting to feel a little left out. Maybe you are, too."
But Obama sought to turn that back on his critics. He said McCain had earlier been "telling me I was supposed to take this trip. He suggested it and thought it was a good idea."
"John McCain has visited every one of these countries post-primary that I have," he said. "So it doesn't strike me that we have done anything different than the McCain campaign has done, which is to recognize that part of the job of the next president, commander in chief is to forge effective relationships with our allies."
The trip was designed by the campaign to show Obama on an international stage in a way that aides hoped would reassure voters who have doubts about his ability to become commander in chief or chart a course for American foreign policy. Jews at home were an audience of particular concern, reflected in his two-night stay in Jerusalem.
McCain has long opposed Obama's call for a 16-month timetable for the withdrawal of U.S. combat troops from Iraq. On Friday, though, McCain said, "I think it's a pretty good timetable, as we should - or horizons for withdrawal," echoing a phrase Bush used in recent days. "But they have to be based on conditions on the ground."
At his news conference, Obama jumped on that to say there was now some convergence "around a proposal that we have been making for a year and a half."
He also said McCain supports sending additional U.S. troops to Afghanistan, "and the Bush administration acknowledges that as well. I have been talking about that since last year," he said.
The senator also said he had canceled a planned trip to visit wounded members of the armed forced in Germany after officials told him a retired two-star general who is an adviser was considered campaign staff and "it would therefore be perceived as political because he had endorsed my candidacy but wasn't on the Senate staff."
He said that as a result, he scrapped the trip to avoid injecting wounded troops into a political controversy.
Obama's final day in Europe included meetings with British Prime Minister Gordon Brown at the official residence at 10 Downing Street and with Conservative Party Leader David Cameron in the opposition party's offices in Parliament. Brown's government is unpopular, and his party recently lost a local election that underscored its weakness.
Still, Obama said he had no advice for Brown. "You are always more popular before you are actually in charge of things. And then, you know, once you are responsible then you are going to make some people unhappy, and that is just the nature of politics," he said.
He also breakfasted with former Prime Minister Tony Blair, now a Middle East envoy.
