U.S. President Barack Obama says he's surprised that Russia's suspension of missile sales to Iran "held this long."
The White House objected earlier this week when Russia announced it would lift a five-year ban on delivery of anti-aircraft missiles.
Moscow says a preliminary agreement over Iran's nuclear program made a 2010 ban on sending missiles to Iran no longer necessary.
Obama said on April 17 that he was surprised Moscow had delayed the decision for so long given the poor relations between Moscow and Washington.
Obama also said the Russian "economy is under strain and this was a substantial sale."
Russia has been slapped with EU and U.S. sanctions for its annexation of Crimea and its alleged support of pro-Russian separatists in eastern Ukraine.
Moscow denies supplying arms, troops and funds to the rebels.