Sen. Tom Udall (D-N.M.) accused the Obama administration of essentially abandoning efforts to secure United Nations support for U.S. action in Syria, drawing a sharp exchange with Secretary of State John Kerry.
The exchange came during Tuesday's hearing of the Senate Foreign Relations Committee on possible U.S. military strikes against forces loyal to Syrian President Bashar Assad.
"I don't believe that we should have given up so easily on using the United Nations," Udall told Kerry, who testified alongside Defense Secretary Chuck Hagel and Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey during the hearing.
"Yes, we have," Udall said defiantly.
"We haven't ... taken Russia to task," the New Mexico Democrat said. "We haven't taken China to task. And that's what we should be pointing out at this point."
Russian and Chinese opposition on the U.N. Security Council to any U.S. action in Syria has forced President Obama to threaten unilateral military action in Syria.
"I know that you're trying very, very hard to find, on the diplomatic side, as secretary of State, a peaceful resolution," Udall added.
While U.S. efforts in the U.N. have been stymied, that was no excuse for Congress not to act, Kerry said, pressing Udall on whether he would be "comfortable" if more Syrian civilians were killed at the hands of the Assad regime.
"Are you going to be comfortable if Assad, as a result of the United States not doing anything, then gasses his people yet again ... and the world says, why didn't the United States act?" Kerry asked Udall.
"History is full of opportunity of moments where someone didn't stand up and act when it made a difference," Kerry said, in a blatant challenge to lawmakers. "That's what's at stake here."
Kerry, Dempsey and Hagel spent more than three hours before the Senate Foreign Relations panel, reiterating the administration's reasoning for military action in Syria.
Their testimony came hours after lawmakers were given a classified briefing on the White House's U.S. operations against the Assad regime, in response to the use of chemical weapons.
Udall was only one of several lawmakers on the panel who posed serious concerns over action in Syria.
Sen. Rand Paul grilled Kerry on whether Congress could depend on Obama to abide by lawmakers' decision if military strikes in the country were voted down.
"I want to be proud of the president, but every time I get just about there, I get worried that he doesn't really mean it," the Kentucky Republican said.
Obama stated he was prepared to conduct strikes against Assad without lawmakers' blessing, in retaliation for the regime's use of chemical weapons. But seeking official authorization from Congress could unify the country behind any effort to strike the Syrian regime.
If the White House dismisses any no vote by Congress on Syria, the president will essentially be making a "joke" out of lawmakers' wishes.
That said, Paul remained unconvinced that U.S. action in Syria would do anything to deter further use of chemical weapons by Assad against anti-government rebels in the country.
Kerry pressed Paul on that point, making clear it was "guaranteed" the Assad regime would be more than willing to attack again if Washington does nothing.
--This report was updated at 10:14 p.m.