North Korean nuclear disarmament talks collapsed here on Thursday after failing to reach agreement on how to determine if the secretive nation had told the truth about its atomic programmes. Chief US envoy Christopher Hill departed Beijing after four days of talks blaming the communist regime for refusing to agree on a protocol to verify a historic declaration it made in June this year about its nuclear activities. "Ultimately, the DPRK (North Korea) was not ready, really, to reach a verification protocol with all the standards that are required," Hill told reporters as he prepared to leave Beijing.