Updated

TOKYO (AP) — North Korea's recent actions indicate it is not yet ready to rejoin multilateral talks aimed at getting it to give up its nuclear weapons program, a senior U.S. negotiator said Wednesday.

Robert Einhorn, the State Department's special adviser for nonproliferation and arms control, said North Korea's recent alleged sinking of a South Korean warship — which Pyongyang denies — and its aggressive rhetoric suggest it is not willing to make serious commitments toward denuclearization.

"I don't know that we are ready today to resume those talks," Einhorn told reporters in Tokyo. "North Korea's actions raise legitimate questions about whether they are willing to live up to their commitments."

Five nations — China, Russia, South Korea, the U.S. and Japan — have been trying for years to convince North Korea to dismantle its nuclear program in exchange for aid and other concessions.

North Korea walked out of those talks last year after being condemned by the U.N. Security Council for firing a long-range rocket. Weeks later, North Korea carried out a nuclear test, its second.

Both nuclear tests resulted in Security Council resolutions, one in 2006 which imposed sanctions and another in 2009 that tightened them.

The U.S. and South Korean accuse North Korea of sinking a South Korean warship in March, killing 46 sailors in the worst military attack on the South since the 1950-53 Korean War.

U.S. Secretary of State Hillary Rodham Clinton announced new sanctions against North Korea during a recent visit to Seoul. Einhorn said on Monday those measures would further isolate the North financially and pinpoint "illicit and deceptive" activities such as drug trafficking, currency counterfeiting and the banned trade in conventional arms.