"As frustrating and as painful, given some of the scenes we’ve seen, we have to pursue diplomacy," said Reed according to a transcript of his interview on Bloomberg's "Political Capital with Al Hunt" airing this weekend.
“We have undertaken interventions in the past that have proved to be extraordinarily expensive, and in some cases counterproductive. I think, and so we have to be very, very careful,” he added.
Syrian President Bashar al-Assad has used brutal force to suppress a year-long uprising from forces seeking the ouster of his regime.
Many Republican lawmakers and presumptive GOP candidate Mitt Romney have called on the administration to arm rebel forces, a policy the White House has rejected.
Reed said in other cases, the West had decided to intervene only after extensive diplomacy had fallen short. He said in regards to Bosnia, "there was a long process of diplomacy, of pulling together the United Nations. It was a United Nations effort. We positioned military force. We did that, but when we went in, it was after exhausting every type of diplomatic approach,” he said.
Reed said there was still a chance Assad would agree to a negotiated settlement that eased him from power, but that Russian involvement was key.
Moscow, a longtime ally of the regime, has blocked United Nations efforts to increase pressure on Assad to step down.
“One of the key elements here is the Russians. … We’re working very hard to get them to recognize that this regime no longer is legitimate in the eyes of the world,” he said.
The Rhode Island senator also said the disjointed nature of the opposition forces weighed against Western intervention.
"There is no coherent, to the point, resistance force," said Reed. "if you’re going to conduct military operations, if it’s the outside alone, the United Nations or a coalition of the willing, and you don’t have an internal force, that makes it all the more difficult."
Many in the administration fear that the opposition forces are too riven by sectarian or geographic differences to form a unified government were Assad to lose power.
In the interview, which also touched on other issues, Reed also defended the Obama administration's increased use of drone attacks against suspected al Qaeda and Taliban militants.
"It is targeted very, very particularly, very carefully against those individuals who have demonstrated a willingness to engage us, attack us, plan attacks against us," he said.
"It’s a policy, and again, it’s a policy that the president continued from President Bush, who began really those operations, particularly in Pakistan. I think both presidents thought that given an enemy that is committed to attacking us, is not non-deterrable, can only be effectively countered by preemption, this is an appropriate way to preempt them."