A bipartisan group of US senators has sent a letter to US Defense Secretary Leon Panetta calling for a boycott of Russian state-owned arms export company Rosoboronexport.

The senators voiced their concern that buying armaments such as Russian-built Mil Mi-17 transport helicopters to supply the nascent Afghan military signals US complicity in the ongoing conflict in Syria. Their letter was dated 12 March.

"[US] taxpayers should not be put in a position where they are indirectly subsidising the mass murder of Syrian civilians," the letter reads. "As such, we urge you to use all available leverage to pressure Russia and Russian entities to end their support of the Assad regime, and that includes ending all [Department of Defense] business dealings with Rosoboronexport, which is within your authority as Secretary of Defense."

The US Army is buying 21 Mi-17s from Russia for $375 million, with the aircraft to be supplied to Afghanistan by 2016. The contract also includes options worth a further $550 million, the letter adds.

The senators also voiced their frustration that the Department of Defense has chosen to supply Afghanistan with Russian-built helicopters rather than US-built machines, and encouraged Panetta to look for alternative sources.

Many of the senators represent states in which major US helicopter contractors and engine-makers have manufacturing facilities.

The letter was signed by senators John Cornyn of Texas, Dick Durbin of Illinois, Kelly Ayotte of New Hampshire, Kirsten Gillibrand of New York, Richard Blumenthal of Connecticut, Sherrod Brown of Ohio, Benjamin Cardin of Maryland and Robert Casey of Pennsylvania.

It was also signed by senators Chuck Grassley of Iowa, Mark Kirk of Illinois, Jon Kyl of Arizona, Robert Menendez of New Jersey, James Risch of Idaho, Marco Rubio of Florida, David Vitter of Louisiana, Roger Wicker of Mississippi, and Ron Wyden of Oregon.

Source: Flight International