WASHINGTON (Reuters) - The State Department said Wednesday that the United States would be open to talking to North Korea  when the time is right  but that it could not happen now because Pyongyang has shown no sign of a willingness to halt its missile and nuclear testing. Despite U.S. Secretary of State Rex Tillerson s offer on Tuesday to start talks with North Korea without pre-conditions, State Department spokeswoman Heather Nauert said there would first have to be a  period of calm  in which Pyongyang suspends  testing before any negotiations could begin. Tillerson, in a speech to a Washington think tank on Tuesday, did not explicitly establish such a freeze as a requirement that North Korea must meet ahead of talks. Nauert, speaking at the State Department s daily briefing, insisted that Tillerson was not establishing new policy in his speech, even though he appeared to back away from a key U.S. demand that Pyongyang must first accept that any negotiations would have to be about giving up its nuclear arsenal. 
North Korea shows no sign it is serious about talking: U.S. official