Lawmakers want President Obama to light into Russia’s Vladimir Putin when the two meet on the margins of the G20 summit in Mexico on Monday.

The meeting, planned after Putin skipped this spring’s G8 meeting at Camp David, marks the first time the two meet face-to-face since Putin regained the presidency in March.

{mosads}Since then relations between the two countries have only gone downhill, reaching a new low with this week’s revelations that Russia is providing President Bashar Assad’s forces in Syria with attack helicopters.

“I think that (Obama) should go to the meeting,” Sen. Kelly Ayotte (R-N.H.) told MSNBC this week, “and take a very, very hard line with Putin and be very clear to him that we are not going to accept Russia continuing to send arms to Syria and that there will be grave consequences to our relationship if they continue that.”

Others are equally adamant that Russia’s continued support for Assad, despite mounting allegations of attacks against unarmed civilians and the risk of civil war, should be front and center.

“When you see what the Russians are doing in terms of sending helicopters to Syria, I think that should be the Number 1 point of discussion,” said Sen. John Barrasso (R-Wyo.), a member of the Senate Foreign Relations Committee.

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The administration has qualified Secretary of State Hillary Clinton’s comments Wednesday about the helicopters, acknowledging that they had been sent to Russia to be refurbished and repaired but weren’t new sales. The distinction didn’t placate lawmakers, however.

“What’s the difference between them being new and them being sent to Moscow and have the blood washed off them and sent back?” Sen. John McCain (R-Ariz.), the top Republican on the Senate Armed Services committee, told The Hill. “I think the secretary of state might have been more specific that these are refurbished helicopters, but they’re still weapons that are massacring Syrians.”

Obama’s top spokesman for national security affairs confirmed Friday that the two leaders will meet on Monday.

Deputy National Security Advisor for Strategic Communications Ben Rhodes said the “reset” between two countries had seen “very positive results” on everything from NATO supply routes to Afghanistan to sanctions on Iran to nuclear disarmament, but acknowledged a “very substantial difference” on the issue of Syria.

“We expect that the agenda for the meeting will cover a range of issues,” Rhodes said. “Syria will certainly be on the agenda of their meeting as well.”

The Republican dean on foreign affairs for his part urged Obama to stay “civil.”

“It’s always advisable to meet with the Russians,” said Sen. Richard Lugar (R-Ind.). “I’m not going to prescribe what the agenda ought to be, but there are a host of things that could be discussed. Specifically right now, obviously, Syria and Iran come to mind, and the implementation of the new START Treaty.”

Sen. Jeanne Shaheen (D-N.H.), a member of the Senate Foreign Relations Committee, agreed.

“Clearly there are a lot of areas where we have overlapping interests and it’s important to communicate,” she said. “I would not presume to tell the president what tone he should use.”

Jeremy Herb contributed