WASHINGTON (JTA) – Two congressmen, a Republican and a Democrat, wrote to U.S. Secretary of State John Kerry to “express our deep concern” that Russia still wants to help Iran expand its anti-aircraft power.

Reps. Ted Deutch (D-Fla.), the senior Democrat on the House Middle East subcommittee, and Peter Roskam (R-Ill.), the bchief deputy majority whip, wrote in a letter dated Sept. 12 that the potential sale of five S-300 air defense systems to Iran “would have devastating implications for Middle East regional security.”

They urged Kerry to reaffirm America’s opposition to the arms transfer while meeting with Russian officials in Geneva this week to broker a Syria deal.

“We ask that you remain steadfast in your opposition,” the congressmen wrote in their letter, saying that if Iran received these systems, “it would significantly expand the military effectiveness of Iranian air power, which will only embolden Supreme Leader Ali Khamenei’s illicit pursuit of nuclear weapons.”

They also pointed out that these missiles could end up in the hands of Hezbollah or the Syrian government.

Russia first agreed to sell the air defense system to Iran in 2007. The sale has yet to go through, in part because of representations to Russia by Israel and the United States. Recent reports suggest that Russia is now tilting toward the sale.