The Chinese military regularly sends ships and aircraft through the channel, Taiwan's defence ministry has said.
The Chinese Embassy in Manila did not immediately respond to a request for comment on the proposed port in Basco.
Cayco confirmed the visit, saying they came "one time to assess" the proposed alternative port.
Marcos has said the bases under the Enhanced Defence Cooperation Agreement (EDCA) could prove useful if China attacked Taiwan.
Jay Batongbacal, maritime affairs expert at the University of the Philippines, said the proposed port "would certainly be needed for the island’s defence in a worst case scenario."
Persons:
Marvin Licudine, Andres Centino, Heather Variava, Noel Beleran, Eric Austin, Marilou Cayco, Batanes, Cayco, Kanishka, MARCOS, Rodrigo Duterte, Ferdinand Marcos Jr, Marcos, Jay Batongbacal, Poppy McPherson, Karen Lema, Raju Gopalakrishnan
Organizations:
Philippine Military, Embassy, Staff, Education, U.S, Reuters, China, Washington, U.S . Army, ., Enhanced, Security, University of the, Thomson
Locations:
Philippines, Philippine, U.S, MANILA, Taiwan . U.S, Taiwan, China, Washington, Pacific, Manila, Basco, Asia, Beijing, Batanes, South China, University of the Philippines, Luzon