North Korea demanded to a senior U.S. envoy that U.N. sanctions imposed on the communist regime for its nuclear defiance be lifted, a report said Wednesday.

North Korean officials made the request to Stephen Bosworth, President Barack Obama's envoy on North Korea, during the diplomat's trip to Pyongyang last week for high-level talks, South Korea's Yonhap news agency reported, citing an unidentified diplomatic source.

South Korean officials in charge of nuclear negotiations were not immediately available for comment.

Bosworth went to North Korea to try persuading the regime to return to disarmament talks also involving South Korea, Russia, China and Japan. He said North Korea agreed on the need to resume the talks but did not make a firm commitment on when it would rejoin the negotiations.

The process had yielded pacts promising North Korea much-needed aid and other concessions in return for step-by-step disarmament. However, Pyongyang walked away from the talks this year in anger over U.N. Security Council condemnation of a rocket launch widely seen as a test of its long-range missile technology.

The U.N. Security Council tightened sanctions in June after North Korea conducted an underground nuclear test, its second, in defiance of an earlier ban. The sanctions, aimed at derailing North Korea's nuclear weapons program, ban the country from developing its nuclear program and selling conventional arms.

The North's reported demand comes as Thai authorities are inspecting 35 tons of weapons seized from a cargo plane loaded in North Korea — the latest known case of Pyongyang's illicit weapons trade in violation of U.N. sanctions.

Thai officials impounded the Ilyushin IL-76 transport plane Saturday after authorities discovered explosives, rocket-propelled grenades and components for surface-to-air missiles.

North Korea is believed to earn hundreds of millions of dollars every year by selling missiles, missile parts and other weapons to countries such as Iran, Syria and Myanmar.