Obama visits Afghanistan to tour war zone

"This is a war that we have to win," he said. "I will send at least two additional combat brigades to Afghanistan, and use this commitment to seek greater contributions — with fewer restrictions — from NATO allies.

"I will focus on training Afghan security forces and supporting an Afghan judiciary, with more resources and incentives for American officers who perform these missions."

By contrast, his opposition to the war in Iraq — and call for an end to the U.S. combat role — helped him overcome his rivals in the battle for the Democratic presidential nomination.

Lately, his efforts to explain how he will use what he learns from U.S. commanders to refine his proposals have brought charges from Republicans and complaints from Democratic liberals that he seems to be shifting his Iraq policy toward the political center. But Obama maintains his basic goal of ending the U.S. combat role soon remains unchanged and that he's always said the U.S. withdrawal must be done carefully.

Obama also arranged to visit Jordan, Israel, Germany, France and England, traveling aboard a jet chartered by his presidential campaign, before his return to the United States. The weeklong trip marks his only foreign excursion as a presidential candidate; McCain has visited Canada, Colombia and Mexico, in part to highlight Obama's opposition to trade deals with those allies.

Obama began his trip with as much secrecy as a presumed presidential nominee can muster.