MOSCOW (AP) -- The arms trade adviser to President Vladimir Putin says Russia has begun delivering S-300 air defense missile systems to Iran, according to the Russian state news agency Tass.

Tass quoted Vladimir Kozhin as saying Thursday that the implementation of the contract for the delivery of the S-300s has begun and the deliveries have started. He didn't provide any specifics.

Russia in 2010 froze a deal to supply advanced long-range S-300 missile systems to Iran, linking the decision to U.N. sanctions. President Vladimir Putin lifted the suspension earlier this year following Iran's deal with six world powers that curbed its nuclear program in exchange for relief from international sanctions. Officials said last month that Russia and Iran finalized the contract for their delivery.

The S-300 deal has long worried Israel and other countries in the region, as well as the U.S., which see it as destabilizing.

By AP