The Chinese will “have to” enforce sanctions against the country if the North Korean nuclear issue is ever going to be solved, U.S. National Security Advisor Robert O’Brien said on Wednesday.

The comments come as Washington and Pyongyang remain stuck in a months-long diplomatic stalemate over the North’s nuclear weapons program, and whether U.S. and UN sanctions currently targeting the DPRK should be lifted or expanded.

China is North Korea’s top trading partner by far, and is viewed by many observers as a weak link in a global sanctions regime that was intended to hurt Pyongyang’s economy.

In his comments