President Trump spoke with China’s leader, Xi Jinping, today about the rising tensions between China and North Korea. This call came after President Trump said that China would need to assist the U.S. in monitoring North Korea in a TV interview.

North Korea is threatening to test its sixth nuclear weapon. A Chinese state newspaper has promised to cut off North Korea’s oil if the country does, and the U.S. is currently sending Navy ships are hovering near the Korean Peninsula in a show of force.

The same Chinese newspaper warned North Korea to not have a “head-on collision” with the U.S. If the country did not cease its nuclear activities, “it may be difficult to have another chance to correct its strategy.”

It’s clear that both China and the U.S. are serious about restraining North Korea’s dangerous behavior. How far will this go, though? Will the United Nations approve sanctions? Will military force be used?