China’s UN ambassador said on Monday it is primarily up to the United States and North Korea, not Beijing, to reduce tensions and work toward resuming talks to end Pyongyang’s nuclear weapon and ballistic missile programmes.

“(The United States and North Korea) hold the primary responsibility to keep things moving, to start moving in the right direction, not China,” China’s UN Ambassador Liu Jieyi told a news conference to mark the end of Beijing’s presidency of the UN Security Council in July.

“No matter how capable China is, China’s efforts will not yield practical results because it depends on the two principal parties,” Liu said. Without naming anyone, he also accused “relevant countries” of violating Security Council resolutions by heightening tensions and failing to resume negotiations.

China’s Vice-Minister of Commerce Qian Keming called on the US to keep China’s trade ties with the US separate from the Korean nuclear crisis.

“We believe that the North Korea nuclear issue and China-US trade are two issues that are in two completely different domains,” he told a press briefing, adding that the issues “are not related, and should not be discussed together”.

US Ambassador to the United Nations Nikki Haley issued a stern warning as she said on Sunday that the US was “done talking about North Korea” and that China must decide whether it would back stronger United Nations sanctions.

“An additional Security Council resolution that does not significantly increase the international pressure on North Korea is of no value,” Haley said in a press release. “In fact, it is worse than nothing, because it sends the message to the North Korean dictator that the international community is unwilling to seriously challenge him. China must decide whether it is finally willing to take this vital step.”

Japanese Prime Minister Shinzo Abe also commented on the issue after speaking to Trump on Monday.

“International society, including Russia and China, needs to take this seriously and increase the pressure,” he said.

Japan and the United States would take steps towards concrete action, he added, without giving details.

Abe and Trump did not discuss military action against North Korea, or what would constitute the crossing of a “red line” by Pyongyang, Japan’s deputy chief cabinet spokesman Koichi Hagiuda told reporters.

The US said on Sunday it shot down a medium-range ballistic missile during its latest test of the country’s THAAD missile defence programme, while South Korea said it would deploy more THAAD units.

China said it had serious concerns about THAAD and reiterated on Monday that all sides should work together for a solution.

Chinese analysts said that the gap between Beijing and Washington continues to widen as both sides are left with increasingly limited options in dealing with the stalemate over North Korea.

“Trump has staked the entire Sino-US relationship on one single issue, which is North Korea[‘s nuclear programme] and his expectations towards China are unrealistic,” said Shi Yinhong, an international relations professor with Renmin University of China and an adviser to the State Council.

He also warned that Washington’s increasing pressure might backfire.

“China is quite worried about its interests being affected by the United States’ secondary sanctions. It would retaliate if the US pushes too far,” he said.

Bonnie Glaser, senior adviser for Asia with the Washington-based Centre for Strategic and International Studies, also said Beijing was not likely to agree to much tougher sanctions at the UN.

“The Chinese believe that missile tests don’t rise to the same threshold as nuclear tests,” she said “They don’t share the US assessment of the urgency of the [North Korea] threat.”

Trump took to Twitter on Saturday saying he was very disappointed in China for not resolving the North Korea problem and that America’s “foolish past leaders” had instead allowed China to make billions of dollars a year in trade.

China’s Bank of Dandong and Chinese shipping firm Dalian Global Unity Shipping Company were targeted by the US government for sanctions last month over accusations of helping North Korea’s nuclear and missile programme and laundering money for Pyongyang.

Trump is expected to sign into law a new sanctions bill targeting North Korea that earned overwhelming support in the US Congress earlier this month.

Lu Chao, a specialist on North Korea at the Liaoning Academy of Social Sciences, said that despite the increasing pressure, it is unlikely that Beijing would cut oil supplies to North Korea or be willing to impose new sanctions on its reclusive neighbour.

He added, however, that China might be compelled to act if North Korea crossed Beijing’s red line in conducting a sixth nuclear test.

Additional reporting by Robert Delaney and Agencies