A bipartisan group of senators urged President Obama on Thursday to end the Pentagon's contractual relationship with a Russian state arms dealer, as tensions between the United States and Russia continue to soar.

Rosoboronexport, Russia's official state arms exporter, has been offered more than $1 billion in no-bid contracts from the Pentagon since 2011 for the procurement of a Russian helicopter called the Mi-17.

“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 percent 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," a bipartisan group of 10 senators wrote.

The arms exporter has also been involved in supplying arms to Syrian President Bashar Assad, the senators write, and "We remain deeply troubled that DoD is sending huge cash payments to an agency that continues to enable mass murder."

The signatories of the letter include Sen. John Cornyn, R-Texas, who has been especially vocal in opposing the Russian helicopter contracts, as well as Sen. Daniel Coats, R-Ind.; Richard Blumenthal, D-Conn.; Chris Murphy, D-Conn.; John Boozman, R-Ark.; James Risch, R-Idaho; David Vitter, R-La.; Roger Wicker, R-Miss.; Kelly Ayotte, R-N.H.; and Mark Kirk, R-Ill.

To impose costs on Russia, the senators argue, the president should cancel existing Department of Defense contracts with the state arms exporter, and ban contracts with any company cooperating with Rosoboronexport on military programs.

"Sanctioning Rosoboronexport would send a powerful message to Putin, and we urge you to give serious consideration to these requests," the senators write.

The Thursday letter follows one earlier this month from lawmakers in the House, who urged Secretary of Defense Chuck Hagel to cancel the Rosoboronexport contract in the wake of Russia's invasion of Crimea.