WASHINGTON — While President Vladimir Putin has been violating a nuclear treaty, arming Bashar al-Assad and closing in on Eastern Europe, Russia’s state-owned arms behemoth has been cashing in on U.S. government contracts.

Arms exporter Rosoboronexport has raked in $1,133,783,077 in Defense Department contracts since 2011, according to federal contracting records. Shortly before these contracts began getting the green light, Rosoboronexport had been the subject of U.S. sanctions for assisting Iran’s nuclear and missile programs.

Since the arms giant supplied Assad with more than $1 billion in deliveries in 2011 alone, Congress leaned on the White House to cut a lucrative no-bid contract with Rosoboronexport to supply the Afghan military with Mi-17 helicopters.

President Obama last year skirted around an amendment passed unanimously by the Senate to prohibit the use of taxpayer dollars to enter into agreements with Rosoboronexport, using a national security loophole to claim that dealing with the Russian firm was in America’s critical interest. As the death toll from Russian arms rose in Syria and protests from both sides of the aisle grew louder, the Pentagon agreed in November to cut its contact with the exporter short and canceled a $345 million order for 15 additional helicopters in Fiscal Year 2014.

Today, senators sent a strong bipartisan message to Obama: cancel all existing contracts with the Russian arms exporter including upcoming deliveries, scrap plans to ink new contracts, and put the company back on the sanctions list where it belongs.

“In light of the Russian Federation’s illegal invasion of Ukraine and annexation of Crimea, we ask for your leadership in re-imposing sanctions on Rosoboronexport, Russia’s official state arms exporter, and fully severing the U.S. Department of Defense’s (DoD) business relationship with this unsavory agency,” wrote the lawmakers. “Since 2011, DoD has awarded Rosoboronexport more than $1 billion in no-bid contracts for the procurement of Mi-17 helicopters. Prior to that, this agency had rightly been under U.S. sanctions for several years.”

The sanctions barring any business with the firm had been placed on Rosoboronexport by President George W. Bush in 2008. When Obama decided to lift the sanctions in May 2010, the administration rejected accusations that they were doing so in an attempt to butter up Russia to support the U.S. position on Iran at the UN Security Council.

“We felt that as Russia shared our concern about Iran and was willing to support the kinds of arms restrictions that are in the draft (UN) resolution, we felt confident that we could remove these penalties while protecting our non-proliferation interests,” then-spokesman P.J. Crowley said at the State Department at the time. “Actions are connected in the sense that clearly the actions Russia has taken over time have demonstrated that they take the situation with Iran seriously.”

Sens. John Cornyn (R-Texas), Dan Coats (R-Ind.), Richard Blumenthal (D-Conn.), Chris Murphy (D-Conn.), John Boozman (R-Ark.), Jim Risch (R-Idaho), David Vitter (R-La.), Roger Wicker (R-Miss.), Kelly Ayotte (R-N.H.) and Mark Kirk (R-Ill.) wrote in today’s letter to Obama that until the invasion of Ukraine, their key concern has been Assad “using these very weapons” obtained from Rosoboronexport “to murder innocent Syrian civilians, as confirmed by DoD.”

“We remain deeply troubled that DoD is sending huge cash payments to an agency that continues to enable mass murder,” they added.

“However, Russia’s recent actions in Ukraine give us a broader reason to put an end to DoD’s misguided business dealings with Rosoboronexport and sanction this agency. Rosoboronexport is an arm of the Russian government and a powerful instrument of Vladimir Putin’s increasingly belligerent foreign policy, and it handles more than 80% of Russia’s weapons exports. By obstructing the business of Rosoboronexport and limiting the income it provides to corrupt Russian officials, we would increase the costs of Putin’s aggression.”