Philippine Navy personnel watch as the US Navy's multipurpose amphibious assault ship USS Wasp cruises in the background during the Balikatan 2019 on Thursday off San Antonio, Zambales. Bulitt Marquez, AP Photo

MANILA - The Philippines' termination of its Visiting Forces Agreement (VFA) with the US might pave the way for Beijing to complete its military bases in the disputed South China Sea, a maritime expert said Monday.

Aside from providing financial assistance and military training, the VFA also deterred the transformation of Scarborough Shoal into an artificial island, according to Jay Batongbacal, director of the UP Institute for Maritime Affairs and Law of the Sea.

China mobilized forces for the shoal's reclamation just before the promulgation of the arbitration ruling in 2016, which invalidated Beijing's sweeping claims in the disputed sea, Batongbacal said.

"That has also been acknowledged by (Defense) Secretary (Delfin) Lorenzana," he told ANC's Early Edition.

"Because there’s VFA, the Americans were able to station 18 warthogs. After Balikatan exercises they stayed on for a while, then these were replaced by FA-18s for a few months."

"Scarborough Shoal is the only piece left in the puzzle that they’re trying to build. They can now completely exclude other countries from the South China Sea militarily if they're able to put into place all of these military bases."

Retired Supreme Court Associate Justice Antonio Carpio earlier warned that China would only agree to a code of conduct in the South China Sea after it has built an air and naval base on Scarborough Shoal.

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President Rodrigo Duterte has ordered officials to notify the US about the VFA's termination, his spokesman earlier said. Defense Secretary Delfin Lorenzana, however, denied such order.

"This tells us really that this move is completely unplanned and undiscussed even though it has been thought of for a long time," Batongbacal said.

"The US-PH alliance has been a problem to China which is President Duterte’s friend, as he calls it."

The US "can't afford to lose the Philippines but they can adjust" their positions in other countries, Batongbacal said.

"If the Philippines doesn’t want the Americans in this region, they will simply adjust to that. After all, they have their own interest to protect," he said.

The Philippines can and should enter into VFAs with other countries but terminating its pact with the US may raise question in its credibility, Batongbacal added.

"We should also have credibility and consistency in our policies," he said.