Tokyo – President Obama arrived in Tokyo on Wednesday to begin an eight-day tour of Asian allies designed to assure leaders that they have a strong U.S. backup at a time of rising tensions in the region.

Obama went directly to his task after landing, heading straight into a private dinner with Japanese Prime Minister Shinzo Abe at a popular sushi restaurant in the busy Ginza shopping district.   

The two leaders will hold more formal talks Thursday, with Obama aiming to promote the U.S. as a committed economic, military and political partner. But the West’s dispute with Russia over Ukraine threatens to cast a shadow over the president’s sales mission.

Obama, whose tour of Asia will also take in South Korea, the Philippines and Malaysia, is the first sitting US president to explicitly affirm that hostile action against the island chain would prompt an American reaction.

“The policy of the United States is clear – the Senkaku Islands are administered by Japan and therefore fall within the scope of Article 5 of the US-Japan Treaty of Mutual Cooperation and Security,” Obama said in a written interview with the Yomiuri Shimbun on Wednesday.