US Secretary of State Hillary Clinton is travelling to Japan at the start of a week long trip to Asia.
Her visit will be dominated by discussions over North Korea after investigators blamed it for the sinking of a South Korean warship.
She will meet the Japanese prime minister to discuss Japan-US ties and the future of the US military base on the island of Okinawa.
Mrs Clinton's trip will also include visits to China and South Korea.
The international report blaming North Korea for the sinking of a South Korean naval vessel in March has raised regional tension.
China, North Korea's only major ally, has urged restraint and has refrained from criticising the North.
But Japan's Prime Minister Yukio Hatoyama called the ship's sinking "unforgivable, an unbelievable act".
Mrs Clinton, her counterpart Katsuya Okada and the Japanese prime minister are also expected to address the dispute over where to move the US Marine Corps' Futenma base on the southern island of Okinawa.
The previous Japanese government agreed that the base was to be relocated to a quieter part of the island.
During campaigning for the election which brought him to power last year, Mr Hatoyama promised to try to move it off the island, a reluctant host to around half the US forces in Japan, our correspondent says.
But it is becoming clear he will be forced to back down, after the US raised operational concerns and other islands refused to take the base.
The China leg of the trip will include the high-level Strategic and Economic Dialogue talks on political and trade issues.