* Pentagon exercises option for 12 more Russian helicopters
* Agreement with Russian arms dealer worth $217.7 million
WASHINGTON, June 13 The Pentagon has notified Congress of plans to purchase more helicopters for the Afghan military from Rosoboronexport, the Russian arms dealer labeled by one U.S. senator as "an enabler of mass murder in Syria," officials said on Wednesday.
The Pentagon ordered two Mi-17 helicopters earlier this year to replace aircraft that crashed, and it decided in recent days to exercise an option to purchase 10 more helicopters to replace aging Afghan aircraft, a Defense Department spokeswoman said.
Total value of the 12-aircraft sale, including engineering services and spare parts, is $217.7 million, the Pentagon told Republican Senator John Cornyn in response to a question.
The purchases this year are part of a larger helicopter contract the Pentagon signed in May 2011 with Rosoboronexport.
The Pentagon has been on the defensive over the agreement with the Russian state arms exporter because of concerns that the firm is also selling attack helicopters to the government of Syrian President Bashar al Assad. There have been reports the government is using helicopters to put down a popular uprising.
Secretary of State Hillary Clinton said on Tuesday that "there are attack helicopters on the way from Russia to Syria." Moscow responded by saying it sold only defensive systems.
The United Nations says Assad's forces have killed more than 10,000 people since the uprising began in March 2011 against his family, which has ruled Syria for four decades.
The initial Pentagon contract with Rosoboronexport was for 21 helicopters, with an option to purchase 12 more. Total value of the deal including spares, engineering services and the 12 optional aircraft was $550 million.
Eighteen of the original 21 helicopters have been delivered and the remaining three should be delivered later this month, the Pentagon spokesperson said.
Cornyn, a member of the Senate Armed Services Committee, said in a letter to Defense Secretary Leon Panetta this week that Rosoboronexport was "an enabler of mass murder in Syria."
"I remain deeply troubled that the (Pentagon) would knowingly do business with a firm that has enabled mass atrocities," Cornyn wrote.
Questioned about Rosoboronexport's arms sales at a news conference on Tuesday, Pentagon spokesman Navy Captain John Kirby defended the Defense Department's actions.
"It's not just what you're flying or where it was made, it's what you're doing with it, right?" he said.
"The helos that we're providing for the Afghan air force are developing a very important capability that country's going to need when the ISAF (International Security Assistance Force) mission ends at the end of 2014," Kirby said. "They're going to need some air force capability."
"And let's not also forget now what the Syrians are doing with their aircraft assets. They're killing their own people," he added. (Reporting By David Alexander, Phil Stewart and Susan Cornwell; Editing by Peter Cooney)