Metro Manila (CNN Philippines) — Brazen lies. This was how a former lawmaker described on Wednesday (September 30) Beijing's pronouncements about disputed waters — based on Chinese President Xi Jinping's recent speech at the White House.

Roilo Golez, who also served as national security adviser during the Arroyo administration, said China was "brazenly lying" about its activities on contested outcrops in the West Philippine Sea.

This developed after Xi, during his first state visit to the United States, told President Barack Obama that China was entitled to build structures on disputed atolls in the Spratly Islands in the South China Sea but did not intend to militarize them.

"Islands in the South China Sea since ancient times are China's territory. We have the right to uphold our own territorial sovereignty and lawful and legitimate maritime rights and interests," Xi said.

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But Golez said this was far from the truth. He cited satellite images that showed apparent militarization on contested islands.

Two weeks before this, the Washington-based Center for Strategic and International Studies (CSIS) said based on satellite images it analyzed, China seemed to be building a third airstrip on Mischief Reef.

Greg Poling, the director of CSIS's Asia Maritime Transparency Initiative, said the structure was similar to airstrips that China had been building on artificial islands at the Fiery Cross and Subi reef in the contested Spratly Islands.

"If it does turn out to be a runway, China will have three airstrips that can carry any plane the PLA (People's Liberation Army) has to offer," Poling said.

The images, taken on September 8, come after China pledged to bring land reclamation in those waters to a halt.

In May, a U.S. surveillance plane carrying a CNN crew was warned eight times by the Chinese navy after it flew over Chinese installations in the area.

Meanwhile, Golez also expressed concern about the United States' diplomatic approach towards China's claims in the West PH Sea.

He said the U.S. Should take a firmer stand instead and increase its military presence in the area by conducting naval patrols.

Golez, who belonged to MARCHA (Movement and Alliance to Resist China's Aggression, added that underestimating China will only lead to full militarization of the disputed territories — leaving no other choice but war.

He said the issue would be raised during the Asia-Pacific Economic Cooperation (APEC) summit in Manila come November.

CNN Philippines' Isabella Montano and CNN contributed to this report.