The Fujian Maritime Safety Administration in southern China only added that the action includes joint patrols and inspections in the central and northern Taiwan Strait.
China began the operation a few hours before the meeting between Tsai and McCarthy in Los Angeles.
The Taiwanese leader is in transit after returning from her trip to Belize and Guatemala.
On Tuesday, the Ministry of Foreign Affairs repeatedly rejected the meeting, demanding Washington respect for the fundamentals of bilateral relations and not allowing official contact with Taipei.
China has been protesting since last week and announced it would take “resolute countermeasures” if talks should go ahead.
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