China National Petroleum Corp. has suspended sales of fuel to North Korea over concerns the state-owned oil company won¡¯t get paid, as pressure mounts on Pyongyang to rein in its nuclear and missile programs, three sources told Reuters.

It¡¯s unclear how long the suspension will last. A prolonged cut would threaten critical supplies of fuel and force North Korea to find alternatives to its main supplier of diesel and gasoline, as scrutiny of China¡¯s close commercial ties with its increasingly isolated neighbor intensifies.

CNPC and the Ministry of Commerce did not respond to requests for comment. China¡¯s Foreign Ministry declined immediate comment. North Korea¡¯s Embassy in Beijing declined to comment.