Taiwan's defence ministry said on Wednesday a Chinese aircraft carrier group was in the waters off the island's southeast coast, the same day President Tsai Ing-wen was due to meet U.S. House Speaker Kevin McCarthy in Los Angeles.
China, which claims democratically-governed Taiwan as its own territory, has warned of unspecified retaliation if the meeting goes ahead.
China staged war games around Taiwan last August following the visit to Taipei of then-House Speaker Nancy Pelosi.
Taiwan's defence ministry said the Chinese ships, which were led by the carrier the Shandong, passed through the Bashi Channel which separates Taiwan from the Philippines and then into waters to Taiwan's southeast.
It said the ships were going for training in the Western Pacific, and that Taiwanese naval and air forces and land-based radar systems closely monitored them.
"The Chinese communists continue to send aircraft and ships to encroach in the seas and airspace around Taiwan," the ministry said.
"In addition to posing a substantial threat to our national security, it also destroys the status quo of regional security and stability. Such actions are by no means the acts of a responsible modern country."
The ministry provided two pictures - one a grainy black and white image of the carrier taken from the air, and the other of a Taiwanese sailor looking at the Shandong and another unidentified ship in the distance.
China has yet to comment on the carrier group, whose appearance also coincided with the arrival in Beijing of French President Emmanuel Macron.
China has sailed its aircraft carriers near to Taiwan before and at similarly sensitive times.
In March of last year, the Shandong sailed through the Taiwan Strait, just hours before the Chinese and U.S. presidents were due to talk.
Taiwan's defence ministry, in its statement about the Shandong's latest mission near the island, said that "external pressure will not hinder our determination to go into the world".
Taiwan's military will continue to closely monitor the situation in the Taiwan Strait, and uphold the principles of "not escalating conflicts, not causing disputes" to deal with any challenges.
(Reporting by Ben Blanchard; Editing by Andrew Heavens)
