US and North Korean officials met at the inter-Korean border last week, and the North Koreans expressed a willingness to resume working-level nuclear talks very soon, a senior US official told foreign media on Tuesday.

A US National Security Council official traveled to the Demilitarized Zone while in the region for "unrelated talks" and met with a North Korean counterpart to deliver photographs from last month's DMZ meeting between US President Donald Trump and North Korean leader Kim Jong-un, Reuters quoted the unnamed official as saying.

During the meeting, the North Korean official said working-level talks on dismantling the regime's nuclear weapons program would restart very soon, Reuters reported.

The AP quoted the US official as relaying that the North Korean official expressed a willingness to resume the negotiations very soon, without committing to any date.

Trump and Kim agreed during their June 30 meeting to revive working-level discussions that had stopped following their no-deal summit in Vietnam in Feb.

But the North test-fired two short-range ballistic missiles last week in what it said was a warning to South Korea for planning joint military exercises with the US next month.

The launches occurred a day after US National Security Adviser John Bolton had visited Seoul with his staff, raising the possibility of a DMZ visit by Matthew Pottinger, the NSC senior director for Asia, or Allison Hooker, the NSC director for Korea.

Trump has brushed off the launches, saying they involved only short-range missiles and that the North hadn't directed the warning to Washington.

He insisted Tuesday that his relationship with Kim remains good.

"My relationship with Kim Jong-un is a very good one, as I'm sure you've seen," Trump told reporters at the White House. "We'll see what happens. I can't tell you what's going to happen."

The Feb. summit collapsed due to disagreement over the scope of North Korea's denuclearization and sanctions relief the US would give in return.

US Secretary of State Mike Pompeo has said that he expects the working-level talks to start again in a couple of weeks. (Yonhap)