“We would like to see more action faster and more obvious and quick results. But I think we’re not giving up yet,” said Susan Thornton, acting assistant secretary of state for Asian affairs. “What we are trying to do is galvanise this pressure and isolate North Korea so it can see what the opportunity cost is over developing these weapons programmes.”

In Beijing on Thursday, Wang underscored China’s opposition to North Korea’s launch of an intercontinental ballistic missile (ICBM) last Friday, saying it was in violation of UN Security Council resolutions.

“At the same time, we also call on all parties not to take any actions that will lead to an escalation in tensions,” Wang said.

Nikki Haley, the US ambassador to the UN, has been discussing a proposed sanctions resolution with Chinese officials since North Korea launched its first ICBM on July 4.

But China, North Korea’s main ally and trading partner, has not yet agreed on the new measures, despite renewed concerns from last week’s missile test.

Dr James Tang, an international relations expert at Singapore Management University, said there was room for China to accept sanctions as a part of the US push for more pressure on North Korea, since relevant parties were “dancing around” trying to avoid military action.

“This is a delicate time,” Tang said. “China probably might come along a bit, but is probably not willing to push too far and threaten the collapse of the North Korean regime.”

But China’s ability to cooperate has been complicated by the inconsistency and ambiguity of the US’ North Korean policy, according to Sun Xingjie, an expert in Chinese diplomacy at Jilin University.

“The US government’s attitudes towards denuclearisation on the Korean peninsula are many and varied, there is no unified voice on this issue,” he said. “China cannot cooperate with the US when it doesn’t know what the US position is. It’s hard to say if Tillerson is even representing [US President Donald] Trump.”

Richard Hu, an international relations specialist at Hong Kong University, said North Korea was one of the most urgent regional security issues for parties at the Asean summit.

“Most people are against North Korea’s provocative actions, but the thing is the strategy and what kind of approach we should adopt,” Hu said. “I don’t think it is solely China’s responsibility to get Pyongyang under control or change their behaviour.”

Thornton did say China had taken unprecedented steps to increase pressure on its neighbour but it could do a lot more to enforce existing sanctions and to impose more.

Her remarks contrasted with those of Trump, who on Saturday accused Beijing of doing nothing to help on North Korea and pointed to the huge US trade deficit with China.

Thornton said Tillerson, due in Manila on Saturday, had no plans to meet North Korea’s foreign minister at the gathering, but he would press China on other issues relating to competing territorial claims in the South China Sea.

Agence France-Presse, Reuters

Additional reporting from Kinling Lo