The visiting US Vice President Joe Biden and Japanese Prime Minister Naoto Kan on Tuesday agreed to strengthen cooperation on reconstruction after the March 11 earthquake and tsunami. "We reiterate our gratitude for the enormous assistance of the United States," Kan told Biden during the first part of the talks, which was open to the press. Biden replied that "our only regret is that we could not even do more" in the wake of the disaster. The premier also said he hoped the vice president's visit would be a "good chance to demonstrate to the world that Japan is open for business." Biden, the first US vice president to visit Japan since Dick Cheney in February 2007, arrived at midnight Monday for a three-day stay. The premier also told Biden that Japan would continue cooperating with the United States and South Korea on North Korea's nuclear weapons programme, Kyodo News reported. Biden was to travel to Sendai, around 200 kilometres north-east of Tokyo, in the afternoon to deliver a speech on Japan's recovery and reconstruction at its tsunami-hit airport. The vice president was to also thank US civilian and military personnel for their assistance in responding to the disaster.