U.S. President Barack Obama welcomed Naoto Kan as Japan's new Prime Minister, the White House said Friday. National Security Council spokesman Mike Hammer said U.S.-Japanese relations are crucial to peace and prosperity in the Asia-Pacific region and that Obama will work closely with Kan on a range of common issues. Kan was named Prime Minister on Friday, becoming Japan's sixth leader in four years. His predecessor Yukio Hatoyama, resigned earlier this week.