The top U.S. negotiator to talks on North Korea's nuclear program is warning that a long-range missile test by Pyongyang could seriously derail six-party nuclear talks.

Christopher Hill

Speaking at a Congressional subcommittee hearing, Assistant Secretary of State Christopher Hill said that Washington is prepared to return to six-party talks.

But he said the North Korean government is mistaken if it believes that a missile test would strengthen the regime's security. He said it would have the opposite effect.

Recent satellite images show a missile on a North Korean launch pad apparently being prepared for launch. But a senior U.S. Senator John Warner has said the latest pictures indicate a launch is not imminent.

Experts say the missile in question has a range capable of reaching parts of the United States.

North Korea last tested a missile in 1998. The rocket crossed Japanese territory before plunging into the Pacific Ocean.

Pyongyang has demanded the United States end a financial crackdown on companies linked to North Korea before it agrees to further six-party nuclear talks. The U.S. has refused, saying the issues are unrelated.