A U.S. diplomat handling Korea affairs said Wednesday that Washington is willing to "constructively engage" with Pyongyang if it ceases provocation.

Jim Zumwalt, deputy assistant secretary of state for East Asian and Pacific affairs, stressed that the U.S. is not interested in talks for the sake of talks.

"The United States is prepared to engage constructively with North Korea, but its new leadership must understand that there will be no rewards for provocations," he said at a congressional hearing.

He was defending the Obama administration's policy on the recalcitrant nation against criticism from mostly Republican members of the House Subcommittee on Asia and the Pacific, led by Rep. Donald Manzullo (R-IL).

He urged North Korea to choose a different approach. The communist nation fired a long-range rocket in April, virtually terminating a Feb. 29 agreement with Washington.

The deal called for Pyongyang to suspend some of its nuclear activities and impose a moratorium on ballistic missile launches and nuclear testing.

Multiple reports, based on satellite images, say that the North seems to be preparing for its third nuclear experiment.

Zumwalt said the U.S. is "very frustrated" with the lack of progress in talking with North Korea.

But the U.S. remains "determined and prepared" to resume a dialogue if the nation changes its attitude.

He also reiterated the administration's concern for the well-being of the North Korean people.

"We remain deeply concerned about the dire human rights situation in North Korea," he said.

Regarding the ongoing nuclear negotiations between the U.S. and South Korea, Zumwalt struck an upbeat note.

He sidestepped a question on the possibility of a failure to reach an agreement by 2014, when the existing pact, signed in 1974, expires.

It bans South Korea from reprocessing nuclear waste from about two dozen reactors using U.S.-supplied nuclear materials.

Seoul wants Washington to allow the expansion of its nonmilitary activities to meet its enhanced status as a nuclear energy producer.

Zumwalt said the two sides are now concentrating on ways for successful negotiations.

He emphasized that the U.S. hopes South Korea's civil nuclear industry will prosper, which will be also beneficial to its American counterpart, given their close partnerships.

He indicated that U.S. worries over proliferation could lengthen the negotiations.

"We also -- of course, South Korea shares this concern with us-- have concern about proliferation of materials that could be used in manufacturing nuclear weapons," he said.

Asked about South Korea's reported ambition to acquire its own nuclear deterrence, meanwhile, he said there have been no such discussions, with the U.S. security commitment to the area very clear.

After the hearing, he hurriedly left the venue, refusing to take reporters' questions.

A career diplomat with expertise in trade, economy and East Asia, Zumwalt has been in charge of Korean and Japanese affairs at the State Department since January.

(Yonhap)