Clinton and Pentagon chief Leon Panetta urged the Senate on Wednesday to ratify a UN treaty on the law of the sea, arguing it was vital for the country's economic and military interests.
President Barack Obama's administration has launched a fresh push for approval of the treaty, saying major US industries are losing out on commercial opportunities and Washington's diplomatic leadership is being undermined by the Senate's failure to ratify the convention.
"We are on the sidelines," Clinton told the Senate Foreign Relations Committee.
"We believe it is imperative to act now," she said.
Both Clinton and Panetta said the treaty was needed to bolster US credibility as it seeks to counter Beijing's claims in the South China Sea as well as Iran's threats over oil shipping in the Strait of Hormuz.
