WASHINGTON—“There should be no doubt about resolve of the United States. We stand by our allies and we stand by our commitments,” Assistant Secretary of State Daniel Russel, the top US diplomat for East Asia, told a Senate panel that oversees policy in the region.

The United States on Thursday cautioned China that it will meet its defense commitments to allies as tensions mount between Manila and Beijing over their territorial dispute in the South China Sea.

Russel told a congressional hearing that some Asian countries fear that Russia’s annexation of Crimea could serve as a precedent for Beijing.

In China’s most recent assertive display, its Coast Guard ships attempted to interdict a Philippine vessel resupplying a small offshore garrison on the BRP Sierra Madre at Ayungin Shoal (Second Thomas Shoal) on the Philippine side of the Spratly archipelago in the South China Sea on March 29.

The Philippines is a US treaty ally and one of several nations with conflicting territorial claims with China over small islands and reefs in the South China Sea, most of which China claims for itself.

Russel said China’s “intimidating steps” toward the Philippines appeared to reflect its “anger and discontent” over the Philippines filing a case at the United Nations arbitral tribunal in The Hague, the Netherlands, on Sunday challenging China’s claims.

“It is incumbent of all the claimants to foreswear intimidation, coercion and other nondiplomatic or extralegal means,” Russel said.

He urged China to clarify its claims in the South China Sea and reiterated US support for a diplomatic solution.

Brunei, Malaysia, Vietnam and Taiwan also have territorial claims in the 3.5-square-kilometer South China Sea, 90 percent of which China insists is part of its territory.

China says its claims in the South China Sea have a solid historic and legal basis although they extend into the 370-km exclusive economic zones of other nations.