The United Nations Security Council is set to vote Wednesday to impose new sanctions on North Korea for its fifth and largest nuclear test, slashing Pyongyang's export earnings by some $800 million, diplomats said on Monday.

Diplomats said the council's five veto-wielding powers — the United States, China, Britain, Russia and France — had agreed to new measures, seen by Reuters on Friday, that largely target the hermit Asian state's coal export earnings.

"We didn't get everything we wanted," said a U.S. official familiar with the draft resolution, though he added the proposed new sanctions were "pretty good."