The United States pressed China to exert more economic and diplomatic pressure on North Korea to help get control over its nuclear and missile programs amid a series of high-level talks in Washington.

The meeting on Wednesday of top US and Chinese ambassadors and protection chiefs was held a day after President Donald Trump said Chinese efforts to utilize its leverage with Pyongyang had fizzled, raising crisp questions about his administration’s strategy for countering the threat from North Korea.

“We repeated to China that they have a diplomatic responsibility to exert considerably greater economic and diplomatic pressure on the regime on the off chance that they need to prevent advance escalation in the region,” US Secretary of State Rex Tillerson told reporters at a joint news meeting with Defense Secretary Jim Mattis.

Mattis vowed to “continue to take essential measures to protect ourselves and our allies” against North Korea, which is attempting to build up a nuclear-tipped missile fit for hitting the United States.

In any case, with the long-standing choice of pre-emptive military strikes seen as extremely hazardous for the present, Trump’s associates are pushing economic and diplomatic pressure.

Tillerson said Trump would make a state visit to China this year, and Mattis said both sides consented to grow military-to-military ties, signaling the new administration’s assurance to continue efforts to enhance relations between the world’s two biggest economies, in spite of dissatisfaction over North Korea.

Trump on Wednesday said the United States had an “incredible relationship with China”.

North Korea bested the agenda at the recently established Diplomatic and Security Dialog, which combined Tillerson and Mattis with Chinese State Councilor Yang Jiechi and General Fang Fenghui, head of joint staff of the People’s Liberation Army.

While the US officials focused on agreement on the objective of North Korean denuclearisation, the talks additionally managed China’s broad territorial claims in the South China Sea, with the Americans reaffirming resistance to Beijing’s militarisation of islands it is working in the strategic waterway.

Tillerson asked China to enable crack to down on illicit North Korean exercises that fund its nuclear and missile programs. Tillerson focused on the need to interfere with funding sources including illegal tax avoidance, work export, and computer hacking.

“Nations around the globe and in the UN Security Council are participating in this exertion, and we trust China will do their part also,” he said.

China’s Foreign Ministry said before Beijing had made “unremitting efforts” to determine strains on the Korean peninsula for its own interests, not because of external pressure.