MANILA -- Beijing will sign a code of conduct seeking to manage tensions in the South China Sea only after it has built an air and naval base on Scarborough Shoal, retired Supreme Court Associate Justice Antonio Carpio said Monday.

Carpio said the base would allow Beijing to “plug the loophole” in its “strategic plan to control the South China Sea for economic and military purposes.”

China earlier built military facilities on reclaimed land in the Spratlys, despite protests from other claimant countries such as the Philippines and Vietnam.

“After China completes its air and naval base on Scarborough Shoal, (it) will then announce it is ready to sign the code of conduct,” Carpio told a Makati City forum.

Carpio said the new code could then prevent any new construction in the disputed waters.

Unless the deal includes an “express reservation,” he said “all prior reclamations and island-building by China will gain de facto recognition by other disputant states.”

“This is the scenario China considers as the appropriate time to sign a code of conduct,” he said.

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Negotiations have dragged on for 17 years since the Association of Southeast Asian Nations signed a non-binding declaration with Beijing governing their conduct in the South China Sea.

The goal was to convert the declaration into a legally binding code to minimize tensions in the important waterway.

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But China, analysts said, became more open to the idea only after its furious island-building over the past several years.

China and the regional bloc are negotiating details of the sea code, which they hope to finish by 2022.

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Beijing sees the last 3 years of President Rodrigo Duterte in office as a “window of opportunity” for the construction on Scarborough, Carpio said, citing the administration’s reluctance to offer even “token resistance.”

“China knows that this is the policy of President Duterte but China is not sure if the next Philippine president will adopt the same policy,” he said.

“So, China will have to make its move before the end of President Duterte’s term.”