Tokyo: Barack Obama insisted on Friday that the US was a “Pacific" power and vowed to deepen its engagement in the region as he set foot in Asia for the first time as US President.

“The United States will strengthen our alliances, build new partnerships and we will be part of multilateral efforts and regional institutions that advance regional security and prosperity," he said in Tokyo as he launched his four-nation tour.

New partnerships: Barack Obama (left) and Yukio Hatoyama in Tokyo. Pablo Martinez Monsivais / AP

The US President’s trip, just over a year after he won the election to the White House, is designed to shore up US power in a region increasingly dominated by rising giant China.

Obama seeks to counter charges that US influence has frayed in Asia, with Washington distracted by its deep economic slump and the sapping wars in Iraq and Afghanistan.

In Tokyo, he promised Americans a “transparent" decision soon on whether to send thousands more troops to Afghanistan, after apparent divides within his administration on strategy were leaked to the press.

The US President also sought to ease a simmering row with Japan over US bases on the southern island of Okinawa, where the US military presence is intensely controversial and has strained ties between the decades-old allies.

Hatoyama has voiced admiration for Obama and stressed similarities between their Democratic parties, which both defeated conservative governments on a promise of change.

The leaders also agreed to work together to battle climate change and the spread of nuclear weapons, including the threat posed by North Korea, which has in the past test-fired missiles across the Japanese islands.

Obama and Hatoyama said they “aspire to reduce" each nation’s greenhouse emissions by 80% by 2050, and to seek a global cut of 50% by then—matching a goal set by the Group of Eight rich nations.

Asked whether he would visit Hiroshima and Nagasaki, the cities destroyed by US atomic bombs in World War II, Obama said: “I certainly would be honoured, it would be meaningful for me to visit those two cities in the future."

On the next leg of his trip, Obama will meet many regional leaders for the first time at the Asia-Pacific Economic Cooperation (Apec) summit in Singapore.

He will also become the first US President to sit down with all 10 leaders of the Association of Southeast Asian Nations, including US foe Myanmar.

Obama will then head to China in the three-day centrepiece of his tour, with top global security issues, along with trade and currency differences, on the agenda, before wrapping up his trip in South Korea.

But he will not specifically mention Tibet in his speech on Asia policy on Saturday, a senior aide said, following claims Washington has downplayed the issue to avoid angering China.