TOKYO (AFP) - Japan and the United States on Saturday agreed to continue talks on ways to boost the nuclear deterrence Washington provides to Tokyo as tensions continue with North Korea, officials said. The US delegation led by Kurt Campbell, assistant secretary of state for East Asian and Pacific affairs, and Wallace Gregson, assistant secretary of defence discussed with their Japanese counterparts the situation in North Korea and the Japan-US security alliance, they said in statements. We agreed to consult closely on the Japan-US security alliance including the nuclear deterrence under the '2 plus 2 framework, the Japanese foreign ministry said in a statement, referring to the bilateral talks comprising both countries foreign and defence ministries. We are in a period right now of intense consultation among the allies over the North Korean nuclear programme, Campbell told reporters after the meeting. The issue of a so-called nuclear umbrella when a nuclear power pledges to defend an ally that is not armed with atomic weapons is sensitive in Japan, the only country to have suffered an atomic attack. Washington and Tokyo have long shied from officially discussing the issue, even though a Japanese official said the issue had been occasionally discussed in closed-door bilateral talks. Japan campaigns for a world free of nuclear weapons but relies on the United States for deterrence as fears mount over North Koreas atomic programme and Chinas continued stockpiling. Campbell arrived in Japan on Thursday for talks with Japanese Foreign Minister Hirofumi Nakasone and other high-level officials that focused on North Koreas nuclear and missile tests as well as the maintenance of the Japan-US security alliance.