North Korean leader Kim Jong-un, front, watched the regime's new tactical guided missile firing on Tuesday, according to the Korean Central News Agency, in August 2019. Yonhap

A senior U.S. official warned Friday that the chances of diplomatically ending North Korea's nuclear weapons program were growing slim.

Speaking to reporters in a background briefing, the senior State Department official said he had delivered the message to Chinese officials on a recent trip to Beijing.

"I urged Beijing to maintain pressure on the regime, noting the space for a diplomatic solution is quickly closing; and that Beijing must take action to prevent sanctions evasion that occurs in its jurisdiction, such as a failure to stop ship-to-ship transfers of coal and oil that take place in Chinese waters," the official said without elaborating.

The comment comes as denuclearization negotiations between Washington and Pyongyang have stalled since a second summit between U.S. President Donald Trump and North Korean leader Kim Jong-un in February ended without a deal.

The North has stepped up pressure on the U.S. to come up with an acceptable offer before the end of the year as it seeks sanctions relief and security guarantees in exchange for the dismantling of its nuclear weapons program.

Earlier this week North Korea's top nuclear negotiator, Kim Myong-gil, claimed the U.S. had proposed another working-level meeting in December.