In a bipartisan rebuke of the Obama administration’s Syria policy, almost all the members of the Senate Foreign Relations Committee voted Tuesday to authorize arming moderate elements of the Syrian opposition.

Democrats and Republicans alike criticized the Obama administration for not being more active in its efforts to encourage the fall of Syrian President Bashar al-Assad and to support the more secular parts of the Syrian opposition, who could find themselves in another war with extremist groups now fighting alongside them if and when the regime falls. The committee approved a bill (PDF) aimed at increasing the pressure on Assad and supporting the moderate opposition, sponsored by Chairman Robert Menendez (D–New Jersey) and ranking Republican Bob Corker (R–Tennessee).

“The time to act and turn the tide against Assad is now,” Menendez said Tuesday at a hearing on the legislation. “The United States must play a role in tipping the scales toward opposition groups and working to build a free and democratic Syria.”

The bill, which passed the committee 15–3, now awaits action on the Senate floor. It represents the most forward-leaning action by Congress since the civil war in Syria broke out and calls for action far beyond White House pledges, which so far have been limited to nonlethal aid and humanitarian assistance.

The legislation authorizes the administration to arm, train, and give other support to armed opposition groups that have been vetted by the U.S. government. The U.S. government would not be able to give the rebels anti-aircraft systems, but no other restrictions on arming the rebels are in the bill. The bill also would increase arms and oil sanctions on the Assad regime, create a $250 million transition fund for the post-Assad government, and allow sanctions to be lifted after a new government in Syria comes to power.

For the Democrats on the panel, the bill represents a break from the president, also their party leader, born out of frustration with the slow pace of the administration’s action on Syria.

“I have to say I think we all share this, at least the last year if not longer, we’ve all been frustrated that our country hasn’t done enough to be responsive,” said Sen. Bob Casey (D–Pennsylvania). “I think it’s in our national-security interests to address this.”

For the Republicans on the panel, Tuesday’s hearing was the latest instance of the party grappling over whether to embrace a more isolationist stance or return to its traditional identity as the party more inclined to support the projection of American power and influence abroad.

Some Republicans, such as Sen. John McCain (R–Arizona), have long supported increased U.S. action inside Syria. But for others, like Corker, their endorsement of arming some Syrian rebels represents a departure from their long-held resistance to U.S. involvement in the Syrian conflict.

“All of us know that much of the policy around Syria has been done on an ad hoc basis. Basically we have been reacting to the events on the ground,” Corker said. “What this bill does is lay out a strategy, not only to cause the balance to change and to cause Assad to be in a different position ... but what it really does too is focus on the day after.”

Sen. Marco Rubio (R–Florida) also said Tuesday that he supported arming the Syrian rebels somewhat reluctantly but that the rise of the al-Nusra Front, an al Qaeda–affiliated group fighting against the Assad regime, made it necessary for American to arm the other Syrian rebels.

“The U.S. cannot solve every conflict on the planet,” Rubio said. “But I believe it’s in the national interest of the United States to ensure that the strongest, best-organized, and best-funded elements in a post-Assad Syria and even before his fall are interests that are aligned with us and are friendlier to us than the alternative.”

Sen. Rand Paul (R–Kentucky) attempted unsuccessfully to add an amendment to the bill stating that the 2001 authorization of the use of force following the 9/11 attacks does not apply to Syria. He said the Assad regime has been protecting minorities that may be left vulnerable if and when Assad falls and that U.S. arms may very well get into extremist hands.

“In your rush to get involved in Syria, you may be arming Islamic rebels who will be shooting Christians,” he said. “We’re actually arming the side of al Qaeda.”

Corker pushed back against Paul by emphasizing that the idea of arming the Syrian rebels is to counter al Qaeda’s influence, both now and after the war ends.

“It’s the second war now that is of greater concern than even Assad, and that is who is going to control the country the day after Assad,” Corker said. “Sitting on our hands and not getting involved, it’s almost assured that al Qaeda or at least extremists with similar views are going to control the country. That’s what we are trying to prevent.”

Last year, Secretary of State Hillary Clinton and CIA Director David Petraeus presented the White House with a plan to arm some elements of the Syrian opposition that was supported by Defense Secretary Leon Panetta and Joint Chiefs Chairman Gen. Martin Dempsey. The White House rejected the Clinton-Petraeus plan.

Last month, Dempsey testified that the idea of arming the opposition had become more complicated because U.S. understanding of the Syrian opposition groups was not clear.

“My military judgment is that now that we have seen the emergence of al-Nusra and Ahrar al-Sham notably, and now that we have seen photographs of some of the weapons that have been flowing into Syria in the hands of those groups, now I am more concerned than I was before,” he said.

Dempsey added he would support arming the rebels “if we could clearly identify the right people.”