Damascus has evaded international pressure to end its military crackdown on protesters who've demonstrated against the government of Syrian President Bashar Assad since mid-March.
Jeffrey Feltman, U.S. assistant secretary of state for near eastern affairs, in a written statement to lawmakers, said the Syrian people have "an irrepressible hunger" for political change in their country.
Damascus has made a series of pledges of reform that it says appeals to the protesters' demands.
Feltman said armed resistance to the Syrian government was becoming commonplace but warned of playing into the regime's hands.
"By working diligently to channel non-violent opposition into a proto-insurgency, the regime seeks to discredit the opposition, scare minorities into submission, unite security forces against a common enemy, fragment international consensus and tear Syria apart along sectarian lines," he testified.
Human Rights Watch, in a 63-page report published Friday, said it had evidence that in the restive city of Homs there is overwhelming evidence to suggest that the Syrian government has committed crimes against humanity against its own people.
The United Nations has put the protest-related death toll in Syrian at more than 3,500 since the uprising began.