BEIJING, June 1 (Reuters) - China's foreign ministry on Wednesday slammed a joint statement by the leaders of the United States and New Zealand that expressed "grave concerns" on human rights violations in Xinjiang and the erosion of freedoms in Hong Kong.

Their joint statement smears China and gravely interferes in China's internal affairs, said Zhao Lijian, a spokesman at the Chinese foreign ministry.

In their statement, U.S. President Joe Biden and New Zealand Prime Minister Jacinda Ardern also said they would encourage the peaceful resolution of cross-Strait issues.

Taiwan, Xinjiang and Hong Kong are China's internal affairs, Zhao said at a regular news conference.