BEIJING, Jan 16 (Reuters) - A U.S. diplomat's remarks about Nauru breaking ties with Taiwan was "grossly interfering" with China's internal affairs, China foreign ministry spokesperson, Mao Ning, said at a regular press conference on Tuesday.

Nauru on Monday severed ties with Taiwan and established diplomatic relations with China, and the U.S. official, who heads the body that handles America's unofficial ties with Taiwan, on Tuesday decried Nauru's "unfortunate" decision and warned that Beijing's promises often go unfulfilled.

The United States is publicly judging the decision made by a sovereign state and smearing China diplomacy, Mao said. (Reporting by Andrew Hayley and Beijing newsroom; Editing by Tom Hogeu)