A leading defense budget-writer is crafting a plan to stop the U.S. government from doing business with a Russian firm that has supplied arms to the Syrian government.

Rep. Jim Moran (D-Va.), the third-ranking Democrat on the House Appropriations Defense subcommittee (HAC-D), said he plans to propose an amendment to the fiscal year 2013 defense appropriations bill to bar the Pentagon from contracting with Rosoboronexport.

The Russian state-controlled exporting firm has provided aircraft to Syria as well as the United States. The Pentagon has a sole-source contract with the firm to buy Mi-17 helicopters for Afghanistan. Lawmakers have written to Defense Secretary Leon Panetta and proposed legislation reflecting concern about Rosoboronexport, given Syrian President Bashar al-Assad’s military crackdown on his citizens.

Moran said it is unacceptable to him that “the Russian arms firm that is supplying the helicopters and other armaments to the Syrian regime is being subsidized by the American taxpayer.”

“We’re spending about $1 billion to buy helicopters from them to give to the Afghans?…I don’t think we should be doing that, and that’s some leverage we could use with the Russians, who are the biggest problem right now in terms of enabling Assad’s regime,” the Virginia congressman said in a brief interview last week.

When the House debates the FY ’13 defense appropriations measure, as soon as next week, Moran said he wants to offer an amendment to “terminate all purchasing from any Russian arms firm that’s supplying weapons to Assad.” He said the proposed legislative change likely would not name Rosoboronexport, but make clear it is about that company. The exporting firm is responsible for the vast majority of Russia’s foreign arms sales.

The two versions of the policy-setting defense authorization bill for FY ’13 now active in Congress–one approved by the full House and the other by the Senate Armed Services Committee (SASC)–both address Rosoboronexport. The House bill would ban the Pentagon from contracting in the future with companies that provide arms to the Syrian government. The SASC’s bill calls for the Government Accountability Office to investigate the Rosoboronexport Mi-17 contract with the Pentagon.

Senate Majority Whip Dick Durbin (D-Ill.) and Sen. John Cornyn (R-Texas) also joined with 15 other senators in writing a letter to Panetta in March expressing concerns about the Russian firm’s sole-source contract with the Pentagon. The Pentagon has stood by the deal for the Mi-17 helicopters that officials say are the most appropriate for use in Afghanistan.

Organizations including the Project on Government (POGO) oversight have criticized the Pentagon’s dealings with the firm. POGO said the “billions of dollars of lethal aircraft and other weapons” Rosoboronexport has provided the Syrian government may have been used in the slaughter of thousands of Syrian civilians. The U.S. government-watchdog group also is concerned the United States is being overcharged for the Mi-17s and questions if Rosoboronexport is a “responsible contractor.” The United States previously sanctioned the Russian firm over its arms dealings with Iran.

The House Rules Committee cleared the FY ’13 defense appropriations bill for floor debate last Thursday, by approving a so-called open rule for it that allows members to offer any amendments they want on the House floor. The full House approved the rule for the bill last Friday via a 244-176 vote. The House is expected to debate the actual bill next week, after members return from this week’s holiday recess.