U.S. Secretary of State Rex Tillerson increased pressure on North Korea’s largest and most powerful ally, China, on Monday, claiming that they could do more to help curb Kim Jong Un’s pursuit of nuclear weapons and the missile platforms necessary to deliver them to targets around the globe, but Russia’s warming rhetoric toward Kim may  limit China’s influence.

North Korea has violated UN resolutions and international law in their effort to produce miniaturized nuclear warheads that can be mounted on ballistic missiles, as well as a fleet of missile platforms designed to travel at various ranges.  Despite significant international efforts to dissuade Kim from pursuing these weapons, ballistic missile testing has continued unimpeded in North Korea since President Trump took office, though no atomic tests have occurred since last year.

“China and other regional partners should also step up their efforts to help solve this security situation, which threatens not just that region, but really presents a threat to the entire world,” Tillerson told reporters in Sydney after a meeting between the Australian and U.S. foreign and defense ministers.

“We desire productive relationships, but we cannot allow China to use its economic power to buy its way out of other problems, whether it’s militarizing islands in the South China Sea or failing to put appropriate pressure on North Korea,” he said.