The U.S. Department of Defense has accused China of not using its influence over North Korea in a “constructive way,” urging the country to take stronger sanction enforcement measures.

Pentagon Press Secretary John Kirby delivered the assessment in a press conference on Monday after China, along with Russia, circulated a draft proposal to members of the U.N. Security Council (UNSC) late last month calling for loosening sanctions against North Korea.

The press secretary also called on Beijing to “put some bite” into U.N sanctions already in place in order to “help steer North Korea toward a diplomatic solution” to denuclearization,