President Barack Obama and Japanese Prime Minister Shinzo Abe shake hands before having dinner at Sukiyabashi Jiro sushi restaurant in Tokyo, Wednesday, April 23, 2014. Opening a four-country swing through the Asia-Pacific region, Obama is 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.

TOKYO — President Barack Obama opened a trip to Japan today with a close-up look at the art of sushi making at a tiny Tokyo restaurant with hard-to-come-by reservations and a hefty price tag.

Shortly after arriving in Tokyo, Obama joined Japanese Prime Minister Shinzo Abe at Sukiyabashi Jiro, an underground sushi restaurant run by 88-year-old Jiro Ono. The outing was unusually informal by Japanese standards and underscored the effort by both countries to strengthen the personal relationship between Obama and Abe.

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.

Relations between neighbors Russia and Ukraine remain tense nearly a week after both countries, the U.S. and the European Union inked an agreement in Geneva calling on Moscow to use its influence over pro-Russian forces to have them lay down their arms and end their occupation of government buildings in eastern Ukraine. Each side accuses the other of failing to uphold its end of the deal.

The White House, which lays the blame squarely on Russia and praises Ukraine for behaving responsibly, has said it is monitoring the situation closely and is prepared, without being specific about a timeline, to slap additional sanctions on Russia “in the coming days” if it fails to abide by the terms of the tenuous deal.

The U.S. response in Ukraine has unsettled some Asian countries, leaving them to wonder how reliable a partner the U.S. would be if they ever faced a similar situation given their own sea and air disputes with China. Ahead of his arrival in Tokyo, Obama sought to reassure Japan that its security pact with the U.S. does apply to the islands at the center of a territorial dispute with Beijing.

“The policy of the United States is clear,” he said in a written response to questions published in Japan’s Yomiuri newspaper before his arrival in Tokyo at the start of a four-country Asia tour.