WASHINGTON (AP) — Secretary of State Rex Tillerson is criticizing China over its oil supplies to North Korea and Russia for using North Korean laborers.

Tillerson called on the two world powers with the closest economic ties to North Korea to increase pressure over the pariah nation's nuclear and missile programs, and go beyond full implementation of U.N. sanctions.

Tillerson said that continuing to allow North Korean laborers to toil in "slave-like conditions" for wages used to fund nuclear weapons "calls into question Russia's dedication as a partner for peace."

He said that with crude oil still flowing into North Korean refineries, the U.S. also questions China's commitment to "solving an issue that has serious implications for the security of its own citizens."

Tillerson was addressing the U.N. Security Council Friday.