President Obama wraps up a weeklong Asia trip on Friday with a historic visit to Hiroshima, Japan. Obama will be the first sitting president to visit the city synonymous with the deadly nuclear age that began there more than seven decades ago.

Obama said he plans to "honor all those who were lost in World War II and reaffirm our shared vision of a world without nuclear weapons."

Japanese Prime Minister Shinzo Abe, who will accompany Obama, told reporters the trip "will no doubt create further, powerful momentum" toward that goal.

Some 140,000 people died in Hiroshima after the U.S. dropped an atomic bomb on the city on Aug. 6, 1945. A second bomb was dropped on Nagasaki three days later, and Japan surrendered six days after that.

White House officials stress that Obama will not apologize for the bombing nor second-guess President Truman's decision to use nuclear weapons.

"It's important to recognize that in the midst of war, leaders make all kinds of decisions," Obama told Japanese broadcaster NHK. "It's a job of historians to ask questions and examine them. But I know as somebody who has now sat in this position for the last seven-and-a-half years that every leader makes very difficult decisions, particularly during wartime."

Seventy-one years later, the decision to drop the atomic bombs is viewed very differently in the U.S. and Japan. Americans see the bombing as hastening the end of a costly and deadly war. A survey by the Pew Research Center last year found 56 percent of Americans approve of Truman's decision, while 34 percent disapprove. In Japan, nearly 8 out of 10 people see the bombings as unjustified.

Japanese leaders have been accused of minimizing their own country's conduct during the war. Prime Minister Abe told reporters he has no immediate plans to visit Hawaii this year for the 75th anniversary of the Pearl Harbor attack. Abe noted that he did visit the World War II memorial in Washington last year and placed a wreath in honor of all those who died during the war.

In Hiroshima, Obama is expected to tour the city's Peace Memorial and lay a wreath of his own along with the prime minister.

"Innocent people die in a war, on all sides," Obama told NHK. "We should do everything we can to try to promote peace and dialogue around the world ... We should continue to strive for a world without nuclear weapons."

That goal, which Obama spelled out early in his presidency, contributed to his winning the Nobel Peace Prize. The president acknowledged in his NHK interview that he's made only "modest progress" so far in his campaign against nuclear weapons. He struck an arms control agreement with Russia and made a deal to prevent Iran from developing a nuclear weapon for at least a decade. North Korea continues to press ahead with its own nuclear program. And critics complain the U.S. itself is spending heavily to upgrade its nuclear arsenal.

Obama has said since his first trip to Japan in 2009 that he would like to visit Hiroshima, but the White House was cautious about scheduling the trip, mindful that Republicans have repeatedly accused the president of conducting "apology tours." The administration is especially wary about offending World War II veterans and their families. National Security Advisor Susan Rice met with veterans groups in advance of the trip in an effort to allay any concerns. A spokesman for the Veterans of Foreign Wars declined to comment on what was discussed during that meeting.

Obama is expected to pay tribute to America's World War II veterans when he speaks in Hiroshima, and again on Monday when he observes Memorial Day.

"I could not be prouder of the U.S. military and the force for good that it has been," Obama told NHK. "The last time we had a significant military operation in Japan, it was actually to help Japan recover from the tragedy of Fukushima," when an earthquake and tsunami devastated the Japanese nuclear reactor.

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