After an apparent diplomatic overture from Russia Monday, a group of U.S. lawmakers are working on an alternative congressional resolution to deal with Syria and its use of chemical weapons.

Susan Walsh / AP file photo Republican Sen. John McCain and Democratic Sen. Chuck Schumer are leading Senate work on an alternative congressional resolution to deal with Syria and its use of chemical weapons.

The proposal, led in part by Republican Sen. John McCain and Democratic Sen. Chuck Schumer, could replace the limited authorization of force that a key Senate committee approved last week with a congressional directive to the United Nations, a source familiar with the negotiations said.

The alternative legislation would direct the UN to pass a resolution confirming that chemical weapons were used in Syria. Then UN officials would go in to the civil war-torn country and remove existing chemical weapons caches by a certain time.

If those steps don’t take place, the resolution would then authorize the president to use force.

As Obama prepares to address the nation on Syria, he faces a tough uphill battle in Congress, with a toss-up in the Senate and a large number of House members leaning towards a "no" vote. NBC's Peter Alexander reports.

The new proposal comes after Syrian officials appeared open to a proposal by Russia, Syria’s biggest backer, to negotiate a transfer of the country’s chemical weapons to international control.

A White House official confirms to NBC News that President Barack Obama has agreed to a UN discussion on Russia's proposed diplomatic plan.

Obama has spoken to his British and French counterparts, the aide said, and the leaders agreed "to explore seriously the viability of the Russian proposal to put all Syrian chemical weapons and related materials fully under international control in order to ensure their verifiable and enforceable destruction."

On Monday evening, Senate Majority Leader Harry Reid delayed a planned Wednesday test vote on the authorization of force. An aide cited the possible diplomatic opening as a “major factor” in the decision to delay the Senate vote.

After a meeting between Obama and Senate Democrats on Tuesday, Reid indicated that leaders will wait for new diplomatic efforts to unfold before scheduling any votes on the original authorization of the use of force.

"I'm not guaranteeing anything," he said. "I do know this: Our schedule is being driven by developments that are taking place, not by some artificial timeline that we have here."

Other lawmakers involved in the Senate's new negotiations are Republicans Sens. Lindsey Graham of South Carolina, Kelly Ayotte of New Hampshire and Saxby Chambliss of Georgia as well as Democrats Chris Coons of Delaware, Carl Levin of Michigan and Bob Casey of Pennsylvania.

The senators are discussing the plan with the White House and with Senate Foreign Relations Committee Chairman Bob Menendez.

While lawmakers on both sides of the aisle have pointed to the Russian proposal as a possible path to avoid military involvement in Syria, many have also urged caution.

House Speaker John Boehner – who said last week that he supported Obama’s call for limited military action in Syria – said he remains “skeptical” of the possible diplomatic solution but that a peaceful resolution is “always a better outcome.”

“I'm skeptical of it because of the actors involved -- simple as that,” he told reporters on Capitol Hill.

Reid, saying that Syria has an "extremely, extremely low level of credibility" on the issue of chemical weapons, said Tuesday that a diplomatic action must be swift and verifiable.

"The Assad regime must act, and act quickly to prove their offer is real, and not merely a ploy to delay military action, or the action of the Senate," he said.

NBC's Stacey Klein and Michael O'Brien contributed to this report.

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