North Korea on Tuesday offered to hold direct talks with the United States on its proposal to suspend nuclear tests, and suggested dialogue could pave the way to changes on the Korean peninsula.

The US State Department has rejected Pyongyang's offer to suspend nuclear tests in exchange for a temporary freeze on US-South Korea joint military exercises but said it "remains opens to dialogue" with Pyongyang.

North Korea's Deputy Ambassador to the United Nations An Myong Hun told a news conference that the offer still stands.

"We are ready, the government of the DPRK is ready, to explain its intention behind its proposal directly to the United States," said the envoy.

"We are ready for that, if the United States wants additional explanation about the proposal."

The envoy indicated that the talks could lead to broader engagement.

"If this proposal is put into practice this year, many things will be possible," he said.

"I can't go any further, but many things will be possible this year."

The United States, which has close to 30,000 troops permanently stationed in South Korea, conducts a series of joint military exercises with its key Asian ally every year.

- US urged to be 'bold' -

Seoul and Washington insist the drills are defensive in nature, but they are regularly condemned by Pyongyang as provocative rehearsals for invasion.

"By refusing to accept our proposal, the United States has shown once again that they will continue to increase their military capabilities in South Korea," said An.

"This is absolutely unacceptable and cannot be justified."

The envoy called on the United States to drop its "hostile" policy and make the "bold" choice of opting for a new approach.

North Korea has conducted three nuclear tests -- the last in February 2013 -- and recently threatened a fourth in response to a UN resolution condemning its human rights record.

The North Korean envoy insisted that the proposal to the United States was "a very meaningful and significant offer" that would create an atmosphere conducive to dialogue and cooperation on the Korean peninsula.

The United States and North Korea fought each other during the 1950-1953 Korean War and have no diplomatic relations.

Earlier Tuesday, US officials warned that they were considering other sanctions against North Korea in retaliation for the cyber-attack on Sony, which Washington blames on Pyongyang.

North Korea's deputy ambassador again denied any involvement.

"My country has nothing to do with Sony hacking. It is nonsense," he said, adding that the US administration should provide proof of Pyongyang's wrongdoing.