Federal prosecutors in the US are reportedly stepping up measures against Chinese firms which are involved with North Korea.
US media outlets like The Wall Street Journal are reporting the US Attorney's office in Washington D.C. has obtained warrants to freeze the funds of several companies processed in US banks.
The decision comes as part of a move by the US to step up the pressure on Beijing to limit the country, for which China is a major trading partner.
It's claimed by prosecutors these firms helped to finance Pyongyang's nuclear weapons programme which has created a high degree of unrest between the country and the US.
The judge's order targeted a company called Dandong Zhicheng - who have not commented - and four related firms which allegedly bought coal from North Korea with U.S. dollars.
Prosecutors are building the case in order to acquire the power to seize the funds, among other things, in a move expected to add weight in the US's ongoing dispute with Pyonyang over its nuclear weapons programme.
China has said it would ban exports to North Korea as part of the new sanctions imposed on the latter by the United Nations, but US officials are reportedly frustrated Beijing hasn't shut the firms which control this down.
The two countries have been at odds over how to deal with North Korea, increasing the tension in the ongoing dispute.