"The issue of future nuclear tests is linked to U.S. policy toward our country," Kim Yong-nam, president of the Presidium of the Supreme People's Assembly, said in an interview with Kyodo News in Pyongyang.

"If the United States continues to take a hostile attitude and apply pressure on us in various forms, will have no choice but to take physical steps to deal with that," he said.

Asked whether the DPRK planned to return to the six-party talks, Kim said: "That also depends on the attitude of the United States."

"We cannot attend the six-party talks while various sanctions, including financial sanctions, are imposed on us," he said.

The DPRK claimed on Monday that it had successfully conducted its first-ever underground nuclear test.