As the White House considers stepping up its non-lethal assistance to Syrian rebels, Sen. Marco Rubio, R-Fla., suggested Wednesday that it also consider sending ammunition to the forces fighting dictator Bashar al-Assad.

“We don’t have to give them weapons. I think they have plenty of weapons, quite frankly,” Rubio said in remarks at the Washington Institute for Near East Policy, a think tank. “What the opposition really needs is access to ammunition.”

“That’s a step that I’m prepared to advocate for, the provision of ammunition to resistance groups within Syria that we believe we can build a long-term dialogue with,” he said.

Rubio, a member of the Senate Foreign Relations Committee and a rising voice on international affairs in the GOP, recently returned from a trip to the region that included stops in Israel and Jordan. And he warned that even as the civil war between Assad’s forces and opposition fighters rages on, another conflict is beginning to build: the battle to control Syria once Assad falls.

There are “clear signs of Al Nusra and others laying down lines” to establish control of certain parts of the country and stockpiling weapons “to solidify their hold,” Rubio said, referring to an extremist group that is among the rebels fighting Assad.

The problem for the United States is that the “best-equipped, best-armed factions in Syria are the most radical ones,” he said. “We should want the best-organized and best-equipped and most dominant groups in the opposition to be groups that are friendly to our national interests.”

Rubio does not, however, support airstrikes, as Republican Senate colleagues John McCain of Arizona and Lindsey Graham of South Carolina do, or other forms of direct U.S. military action.

“We’re not talking about American troops on the ground, we’re not talking about U.S. air power, we’re not talking about sending American soldiers or even American trainers into Syria,” he said.

The Washington Post reported Wednesday morning that the Obama administration is preparing to make a policy shift on its assistance to Syria, including sending aid directly to Syrian opposition groups rather than through international institutions like the United Nations. And it is seriously considering expanding the types of aid it provides to include body armor, armored vehicles and possibly military training.

Rubio argued Wednesday that there is a clear U.S interest in hastening Assad’s departure.

“Number one, Damascus, and Syria in general, was a waypoint for global terrorists,” he said. “That alone is reason to do everything we can to get rid of Assad and that environment.” And, he added, “I think the loss of Assad is the ultimate sanction against Iran.”

Rubio said Syria inevitably is “going to be a mess after Assad leaves.” But the “longer this thing goes on, the harder it’s going to be to close this security vacuum in the aftermath,” he added.