The United States has no indication North Korea is ready to return to six-country nuclear talks, despite a Japanese newspaper report that it had agreed to do so, the State Department said on Wednesday. "Not to our knowledge. We have no indication that North Korea has yet agreed to return to the table," State Department spokesman Richard Boucher told reporters. He said the United States remained ready to hold talks without preconditions and urged North Korea to return to the table for "serious discussions." The Japanese daily Yomiuri Shimbun reported that the North had apparently agreed to an early resumption of the talks on its nuclear arms program as early as mid-May in return for the promise of a visit to Pyongyang by China's president. The newspaper quoted as its source an unidentified U.S. official in Washington and said the deal was reached during a visit by North Korea's First Vice-Minister of Foreign Affairs Kang Sok-ju to Beijing that ended on Tuesday. U.S. officials said the administration had a preliminary discussion with the Chinese about Kang's trip but "no full read-out." --more 2315 Local Time 2015 GMT