China’s defense ministry protested Saturday against the passage of a U.S. Navy warship, and Coast Guard cutter, through waters between China (a self-governing island) and Taiwan (a U.S. Navy warship).

The ministry posted a statement on its website calling the move provocative. It stated that it showed the United States was the greatest threat to peace, stability, and creates security risks in the 160-kilometer-wide Taiwan Strait.

The statement stated that “We express strong opposition and condemnation”.

According to the U.S. Navy, Friday’s passage of the USS Kidd and Coast Guard cutter Munro through the Strait was in international waters. Such exercises are seen as a warning to China, which recently conducted drills near Taiwan and has not renounced the use of force if needed to bring the island under its control.

“The lawful passage of the ships through Taiwan Strait shows the U.S. commitment towards a free and open Indo-Pacific,” said the Navy’s Japan-based 7th Fleet.

Taiwan, which is home to 23.6million people, was divided from China in a civil war. This led to the Communist Party taking over the mainland in 1949. Although the U.S. has no diplomatic relations with Taiwan, it maintains a Taipei representative office and is Taiwan’s largest supplier of military equipment.

As the Chinese coast guard patrols around disputed islands claimed by both China and other countries in the South and East China Seas, the U.S. Coast Guard has increased its presence in Asia.

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The 418-foot Munro (127-meters) long Munro arrived in the region in August for what the U.S. Coast Guard called a month-long deployment. It spent two days training with the Aso, a Japanese coast guard vessel, in the East China Sea earlier this week.

The U.S. and Taiwan coast guards held talks this month after the two signed a cooperation agreement in March. China has denounced the agreement.

Saturday’s defense ministry statement stated that Taiwan is an inalienable component of China and that China will not tolerate any interference in its internal affairs.