The United States said Friday it believes North Korea may be preparing a nuclear test as soon as this month, its first since 2017, and renewed an offer of dialogue on ratcheting tensions.
The State Department went public with its assessment amid mounting US frustration with North Korea, which has conducted 14 weapons tests since January.
"The United States assesses that the DPRK is preparing its Punggye-ri test site and could be ready to test there as early as this month," State Department deputy spokeswoman Jalina Porter said, referring to North Korea by its official name, the Democratic People's Republic of Korea.
"This assessment is consistent with the DPRK's own recent public statements," she told reporters.
"We have shared this information with allies and partners and will continue closely coordinating with them as well."
US President Joe Biden later this month travels to Japan and South Korea, where concerns about Pyongyang are expected to be high on the agenda.
A North Korean test could coincide with Biden's visit or with the May 10 inauguration in South Korea of President-elect Yoon Suk-yeol, who has vowed to take a harder line on Pyongyang.
North Korea carried out six nuclear tests before embarking on unusually high-profile diplomacy with the United States, with former president Donald Trump meeting three times with leader Kim Jong Un.
Despite Trump's declarations that the two "fell in love," their meetings produced no permanent agreement on dismantling North Korea's nuclear program.
Pyongyang has shown little interest in resuming negotiations since Trump's departure.
- Dialogue and pressure -
The Biden administration says it is ready to start talks with North Korea without preconditions, but would pursue working-level negotiations and not the pageantry of another summit.
"The United States remains committed to seeking diplomacy with the DPRK and calls on the DPRK to engage in dialogue," Secretary of State Antony Blinken said earlier Friday.
"At the same time, we will continue to address the DPRK's unlawful cyber activities, as well as violations of UN Security Council resolutions."
The Biden administration has sought to step up pressure on North Korea.
The Treasury Department on Friday announced sanctions on the virtual currency mixer Blender.io, saying the service was used by a North Korean hacker group to support weapons programs.
It marked the first US sanctions on a virtual currency "mixer," which is used to conceal participants in transactions involving Bitcoin and other cryptocurrencies.
Officials said the Lazarus Group, a North Korean-backed hacker group, stole $620 million from the online video game Axie Infinity.
The United States has also proposed toughening costs on North Korea through the Security Council.
A draft Security Council resolution presented last month by the United States and seen by AFP would tighten sanctions, including by reducing from four million to two million barrels the amount of crude oil North Korea would be allowed to import each year for civilian purposes.
But the resolution stands little chance of approval as diplomats say there is no support from China or Russia, which hold veto power.
The two powers both have relations with Pyongyang and test ties with Washington, but have occasionally backed action out of exasperation with North Korea.
North Korea's recent tests have included its first of an intercontinental ballistic missile at full-range since 2017.
Last week, while overseeing a huge military parade, North Korean leader Kim vowed to develop his nuclear forces "at the fastest possible speed" and warned of possible "pre-emptive" strikes.