North Korean officials have told their US counterparts that Kim Jong Un is ready to discuss denuclearisation, an assurance that could pave the way for a planned meeting with President Donald Trump, reports said.

It is the first time Pyongyang has made the offer of a summit directly to Washington, after its invitation was previously conveyed through a South Korean envoy.

"The US has confirmed that Kim Jong Un is willing to discuss the denuclearization of the Korean Peninsula," a Trump administration official told The Wall Street Journal and Washington Post on Sunday.

Washington stunned observers when it announced last month it had agreed to a historic first meeting between Trump and Kim, to be held by the end of May.

The North's offer to meet was delivered to the White House by South Korea's national security adviser Chung Eui-yong, who had met Kim during a visit to Pyongyang days earlier.

But Pyongyang has failed to publicly confirm the offer since, beyond a commentary from its state-run KCNA news agency noting the "dramatic atmosphere for reconciliation" with the South and "a sign of change" with the US.

This silence had made US officials nervous that Seoul had overstated the North's willingness to negotiate over its own nuclear arsenal, the Wall Street Journal reported.

US gambit

Many remain skeptical about whether the planned summit can succeed.

It is scheduled to take place without the months of groundwork that usually precedes such meetings.

CNN reported Saturday that secret, direct talks paving the way for the summit were under way between North Korean and US intelligence officials, citing anonymous White House sources.

But no specifics have yet emerged concerning the date or venue of the proposed summit, with a third country such as Mongolia or Sweden under consideration to host the talks, according to multiple reports.

Beyond that, a detailed agenda for the talks will need to be set.

Washington's long-held stance is that it will not accept a nuclear-armed North Korea. That means it wants to see "complete, verifiable, and irreversible" denuclearisation -- a very high bar.

The North has previously demanded the withdrawal of US troops based in the South and the end of the security alliance between Seoul and Washington -- an extraordinary concession that it is hard to imagine any previous US president acceding to.

Diplomatic flurry

South Korea on Monday welcomed the reported offer by the North to discuss denuclearization.

"We are not a directly concerned party since it is something that is taking place between the US and North Korea, but if the reports are true, we view it positively and welcome it," said Nam Sang-kyu, a spokesman at the South's presidential office.

The South will host its own summit later this month between Kim and the South's president Moon Jae-in.

Last week, the two Koreas held a working-level meeting aimed at ironing out protocol headaches and other logistics ahead of the rare inter-Korean summit, due to take place on April 27.

A different group of officials from the two sides met Saturday to discuss setting up a direct hotline between the offices of the leaders of North and South Korea.

Details of the talks were not released but officials from both sides agreed to further meetings on the topic later this week, a spokesman for the South's unification ministry said Monday.

The rapprochement on the peninsula was triggered by the South's Winter Olympics, to which the North sent athletes, cheerleaders and Kim's sister as an envoy.

Kim has since pencilled in the summit meetings with the South and the US, and made his international debut with a visit to Beijing -- his first overseas trip since taking power in 2011.