Barack Obama said Saturday that his weeklong trip to Europe and the Middle East only reinforced his foreign policy views, telling FOX News that his proposed troop withdrawal timetable and other military strategies will stay in place if he is elected president.

Rival John McCain had criticized Obama for setting his policies toward Iraq and Afghanistan before traveling to the two war zones. He argued Obama was stubbornly rejecting the advice of commanders before even meeting with them.

But the Illinois senator said Saturday, shortly before heading home to Chicago, that his observations overseas affirmed he had a grasp of the "broad strategic outlines" before going.

"What happens on a trip like this is, I think, you deepen your understandings," Obama told FOX News' Bill Hemmer in London.

"There was a lot of confirmation of my strategies -- that we need to get more troops into Afghanistan, and that the Iraqis are willing to take more responsibility ... that Iran is a grave threat."

He said his plan to withdraw combat troops from Iraq within 16 months of taking office is one "I will abide by fully," though he will take "facts on the ground" into account during that process.

As the presumptive Democratic presidential nominee took off from London, it was unclear what the immediate impact of his high-profile tour would be.

Though polls have fluctuated slightly, the Gallup tracking poll Saturday showed Obama with a 7-point lead -- up from a 6-point advantage the day before and a 2-point edge the day before that.

Obama told reporters Saturday, after a meeting with British Prime Minister Gordon Brown, that he doesn't expect any immediate political impact and suggested he might even see a dip in the polls. He said the point of the trip was to strengthen partnerships overseas.

But the week of global focus on the U.S. presidential race yielded highs and lows for both candidates.

Obama triggered great excitement in Europe. A record crowd of more than 200,000 gathered to watch him speak in Berlin. French President Nicolas Sarkozy practically endorsed Obama following their meeting Friday in Paris.

For the Illinois senator, the trip was seen as a way to insulate himself somewhat against attacks on his foreign policy experience. Before going, he was fielding criticism because he had never traveled to Afghanistan and hadn't been to Iraq since becoming a presidential candidate.

Obama visited U.S. troops overseas and got an unexpected boost when Iraqi Prime Minister Nouri al-Maliki voiced support for the kind of withdrawal timeline he has advocated. (McCain even said in an interview Friday that was a "pretty good timetable," provided it's based on conditions on the ground.)

But while Obama was away, McCain emphasized his commitment to domestic issues, hitting battleground states and amplifying his criticism of Obama over the Iraq war.

McCain charged that Obama was pandering by opposing the troop surge in Iraq, calling his outlook Friday the "audacity of hopelessness."

He seemed to cast Obama as somewhat aloof in his overseas endeavors.

"With all the breathless coverage from abroad, and with Senator Obama now addressing his speeches to ‘the people of the world,' I'm starting to feel a little left out. Maybe you are too," McCain said in his weekly radio address Saturday.

He continued to jab at Obama for refusing to say the troop surge in Iraq has been a success.

"Senator Obama can't quite bring himself to admit his own failure in judgment," McCain said.

Obama took heat for saying in an interview overseas that he wouldn't support the troop surge, even if he had another chance to do so.

He later told FOX News there is "no doubt" those troops helped quell violence in Baghdad, but that McCain was just trying to "narrow this debate" to the issue of the surge.

Obama also continued to catch flak from McCain's campaign Saturday for canceling a visit to U.S. troops at the Landstuhl Regional Medical Center in Germany.

"For a young man so apt at playing president, Barack Obama badly misjudged the important demands of the office he seeks. Visits with world leaders and speeches to cheering Europeans shouldn't be a substitute for comforting injured American heroes," retired Lt. Colonel Joe Repya said in a statement released by the McCain campaign.

The campaign released an ad Saturday criticizing Obama for canceling the visit. The narrator says McCain puts "country first."

Obama told FOX News the decision to bypass the hospital was not a mistake, and repeated his campaign's claim that the visit would have seemed too political -- since that leg of the trip was being funded by his campaign.

"The last thing I wanted to do is to in any way distract the terrific work that's being done in terms of treating our troops, by getting it fouled up by a bunch of politics," he said.

Meanwhile, McCain met with top advisers and donors Saturday in Sedona, Ariz.

The campaign said in a statement, "We're 100 days out, so it's a great time to talk strategy going forward."

Watch FOX News Monday at 9 a.m. ET to see more of the Obama interview with FOX News.