Exclusive - U.S. warns China it will target firms for illicit North Korea business

WASHINGTON (Reuters) - The United States has warned China it will blacklist Chinese companies and banks that do illicit business with North Korea if Beijing fails to enforce U.N. sanctions against Pyongyang, according to senior State Department officials.

The tougher U.S. approach reflects growing impatience with China and a view that it has not strictly enforced existing sanctions to help curb Pyongyang's nuclear programme, which a U.S. policy of both sanctions and diplomacy has failed to dent.