Congress is trying hard to give President-elect Donald Trump some leverage to pressure the governments of Syria, Russia and Iran to stop their onslaught against Syrian civilians and perhaps strike a deal on a political settlement. If Trump accepts it, he would not only be able to negotiate with Vladimir Putin from a position of strength; he might also save a lot of lives.

The Syrian crisis is set to get worse, not better, in the months ahead as Trump begins his presidency. Syrian dictator Bashar al-Assad and his partners’ victory in Aleppo has created new victims of atrocities and a new wave of refugees, and it will likely embolden the guilty parties to continue slaughtering their way across rebel-held areas absent real international pushback.

As Assad’s army, filled out with Iranian-sponsored militia fighters and covered by Russian airstrikes, plans its next conquest — most likely the rebel stronghold in northern Idlib province — the U.S. government stands on the sideline wagging a finger. Russia no longer seriously negotiates with Secretary of State John F. Kerry, calling those discussions “fruitless get-togethers” and preferring to deal with Turkey instead.

The incoming Trump administration has not spelled out what it plans to do about Syria, although the president-elect has said he has “very strong ideas” on the issue and has been discussing it with Russian President Vladimir Putin. He nominated a friend of Putin’s, ExxonMobil chief executive Rex Tillerson, to be his secretary of state. If Trump plans to make a deal with Moscow, he and Tillerson will need what President Obama never gave Kerry — some leverage to negotiate with. That’s where Congress comes in.

After months of behind-the-scenes wrangling, there is new bipartisan legislation on Syria that combines input from the House and Senate. The legislation, introduced this month by Sens. Marco Rubio (R-Fla.) and Robert P. Casey Jr. (D-Pa.) would sanction the Assad regime, Russia and Iran for war crimes and crimes against humanity in Syria while providing a framework for U.S. assistance to Syria going forward.

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“The course of the Syrian transition and its future leadership may depend on what the United States and its partners do now to save Syrian lives, alleviate suffering, and help Syrians determine their own future,” the bill’s preamble states.

Rubio and Casey updated a Syria bill they had introduced in 2013 and incorporated a sanctions bill named after the Syrian defector known as Caesar that the House passed unanimously last month. The senators also absorbed a bill by Rep. Adam Kinzinger (R-Ill.) aimed at preventing Iran from further destabilizing Iraq.

“It’s time for us to push back against [Iran’s Ayatollah Ali] Khamenei, Assad and Putin as they seek to expand their power across the Middle East, and this sanctions bill is our best chance at doing so,” Kinzinger told me.

The bill would require the administration to report on whether top officials in all three governments are complicit in the ongoing atrocities, including the blocking of humanitarian aid from those in need. If so, they would be sanctioned. If Khamenei, Assad and Putin halt the atrocities, Trump could waive the sanctions.

Congress also wants to sanction large sectors of the Syrian economy and central bank. The legislation would also authorize increased humanitarian aid to Syria, support for local governance, a push for a political transition and a fund to reconstruct the country when the fighting stops. Lastly, the bill would require a report on the efficacy of “safe zones” inside Syria, which Trump has often promised to establish — most recently in a speech Thursday.

Tillerson, who has a long relationship with Russia, has often downplayed the usefulness of sanctions as a businessman. By supporting this sanctions package, Tillerson might just convince Rubio and other GOP hawks, including Sens. John McCain (R-Ariz.) and Lindsey O. Graham (R-S.C.), that he is pivoting from defending the interests of ExxonMobil to defending the national security interests of the country. The legislation is sure to come up at his confirmation hearing.

If Trump and Tillerson don’t like the Rubio-Casey bill, they must explain what other pressures they plan to bring to bear against the Syrian, Russian and Iranian governments. A threat of military force seems unlikely. Kerry discovered that without any leverage, Putin had little incentive to do anything but toy with pleas from the United States.

If Trump rejects the idea of adding pressure on Assad and Russia altogether, he is destined to repeat Obama and Kerry’s mistake of negotiating from a position of weakness. That strategy already contributed to a longer war, a higher body count of innocent Syrians and an increased threat of terrorism spilling into the region and headed to our shores.

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