US worried North Korea could return to nuclear tests, urges dialogue

The United States is concerned North Korea's escalating missile tests could be precursors to resumed tests of nuclear weapons and intercontinental ballistic missiles, a senior US official said, while urging Pyongyang to join direct talks with no preconditions.

North Korea conducted its largest missile test since 2017 on Sunday, sending a suspected intermediate-range ballistic missile soaring into space.

South Korean President Moon Jae-in said a recent flurry of North Korean missile tests was reminiscent of heightened tensions in 2017, when North Korea conducted multiple nuclear tests and launched its largest missiles.

He said the latest launch took North Korea a step closer to fully scrapping a self-imposed moratorium on testing its longest-range intercontinental ballistic missiles (ICBMs), which it hasn't tested since 2017.

A senior official of the Biden administration was asked in a briefing for journalists whether Washington shared the concern that Pyongyang might resume ICBM and nuclear testing.

"Of course, we're concerned," he said. "It's not just what they did yesterday, it's the fact that this is coming on the heels of quite a significant number of tests in this month. And that follows on tests at the end of the year going back to September, of a variety of systems."

"We obviously don't want to see further testing and we've called upon to DPRK to refrain from further tests," he said, referring to North Korea by the initials of its official name.

North Korea's testing spree is a major unwanted headache for the Biden administration as it seeks to head off any plans by Russia to invade Ukraine and contends with relations with China at their worst level in decades.

Under President Joe Biden, Washington has repeatedly sought talks with North Korea but has been rebuffed. North Korean leader Kim Jong Un held three summits with Biden's predecessor, Donald Trump, but the talks did not realise Kim's demand for a removal of sanctions on Pyongyang.

The official said the latest North Korean test was part of an "increasingly destabilising" pattern and in violation of UN Security Council resolutions and therefore international law.

"It requires a response," he said. "You will see us taking some steps that are designed to show our commitment to our allies... and at the same time we reiterate our call for diplomacy. We stand ready and we are very serious about trying to have discussions that address concerns on both sides."

The official did not detail the nature of the response.

Despite urging dialogue, Washington has maintained sanctions on North Korea and imposed more following recent tests and sought to encourage the UN Security Council to follow suit.

However, China and Russia delayed a US bid to impose UN sanctions on five North Koreans Washington has accused of procuring goods for its weapons programs.

Asked whether the United States could secure Chinese and Russian support for new sanctions, the official replied: "Our belief is that they understand their responsibilities as Security Council members to make sure that the Council's resolutions are enforced and the Council takes up its responsibility promote peace and stability in the region."