The US says China should not doubt US resolve in meeting its defense commitments to its allies.
Assistant Secretary of State Daniel Russel's comments today follow Chinese efforts to prevent Philippine vessels resupplying a small offshore garrison in the South China Sea.
The Philippines is a US treaty ally and one of several nations with conflicting territorial claims with China in those waters.
Russel told a congressional hearing that China's neighbours are worried that Russia's annexation of Crimea might serve as a precedent for Beijing.
He said Russia's action has heightened concern, particularly among Southeast Asian nations, about the possibility of China "threatening force or other forms of coercion to advance their territorial interests."
Russel said China needs to demonstrate its commitment to peacefully resolving its territorial disputes.
