MANILA - The United States has vowed to continue "freedom of navigation" operations in the disputed South China Sea amid China's militarization efforts in the area.

Brian Hook, a senior adviser to the US Secretary of State on Asia Policy, told reporters in a phone conference Tuesday that Washington will not accept unilateral actions by claimants that change the status quo in the waters while issues of sovereignty remain unresolved.

Citing satellite images last month, a US think-tank had reported on continuing militarization efforts by China on its man-made islands on the South China Sea.

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The United States has criticized China's construction of islands and build-up of military facilities in the sea and has expressed concerns that these could be used to restrict free nautical movement.

The US military has a long-standing position that its operations are carried out throughout the world, including in areas claimed by allies.

"...What we do is freedom of navigation and overflight to the freedoms of assembly and expression online. These are the things that we will enforce and so we fly, sail, and operate wherever international law permits," Hook said.

Hook described China's militarization of the South China Sea as "provocative" and reiterated US commitment to uphold international law.

"We very strongly believe that China's rise cannot come at the expense of the values and rules-based order... When China's behavior is out of step with these values and these rules, we will stand up and defend the rule of law," he said.

"They (China) are pushing around smaller states in ways that put strains in the global system and their actions also undermine core principles of sovereignty which are very dear to us," he added.

China's sweeping claims in the South China Sea have been met with protests from Brunei, Malaysia, the Philippines, Taiwan, and Vietnam.

The Philippines has raised its claims on the South China Sea to the Hague-based Permanent Court of Arbitration and was favored by the international court in 2016. China, however, has refused to recognize the ruling. --report from Willard Cheng, ABS-CBN News and Reuters

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