Obama is on the first stop of a weeklong trip to Asia in which he will try to re-establish America's role as a leader in the Pacific Rim and persuade China and other Asian nations to open up their own troubled economies to more U.S. exports. Obama met privately with Japanese Prime Minister Yukio Hatoyama before holding a joint news conference to reaffirm their commitment to the half-century-old alliance. Hatoyama seemed pleased with the meeting, saying the two men have taken to calling each other by their first names: 'Barack and Yukio.' The bond between the U.S. and Japan has been strained of late. Hatoyama heads a new Japanese government that has signaled that the country's future may depend more on other Pacific Rim nations than the United States. At the same time, residents of Okinawa have called for the removal of a U.S. Marine base on the island -- a position that Hatoyama supported as a candidate for office. At the news conference, the two leaders downplayed any differences. They said a high-level working group is trying to resolve the Okinawa dispute. 'Our goal remains the same and that's to provide for the defense of Japan with minimal intrusion on the lives of the people who share this space,' Obama said when asked about the base. The American president sidestepped a question from a Japanese reporter who asked if dropping atom bombs on Hiroshima and Nagasaki at the close of World War II was the right decision, discussing instead the international communities' concerns about North Korea. Obama plainly wanted to avoid an issue that has bedeviled historians and policymakers for decades: Was the U.S. right to drop the atom bomb, or was there a way to end the war with less destruction? Obama and Hatoyama emphasized the agreements they had reached on climate change and nuclear nonproliferation. They issued a joint statement calling for 'a world without nuclear weapons.' And they said they 'aspire' to reducing carbon emissions 80 percent by the year 2050. Obama also drove home a message he will repeat throughout his tour of the region: The U.S. is determined to be an active player in Asia, even as China's economic and military influence grows. 'I intend to make clear that the United States is a Pacific nation, and we will be deepening our engagement in this part of the world,' Obama said. Before leaving Washington on Thursday for the seven-day, four-nation trip, Obama signaled that he would press Asian leaders to open up their markets and boost purchases of U.S. goods instead of relentlessly focusing on exporting more and more to American consumers. Times staff writer Nicholas reported from Washington and staff writer Lee from Tokyo. Staff writer David Pierson in Beijing contributed to this report. 