Russia says there has been no date set yet for the delivery of the advanced S-300 missile defense system to Iran.

Russian Deputy Foreign Minister Sergei Ryabkov, who has been heading up the delivery organization of the weapons system to Iran, said that he could not “say anything for now” about when the missiles’ delivery date might be, according to Russia’s Interfax News Agency.

Initially signed in 2007, the $800 million deal between Iran and Russia for the S-300 system was put on hold in 2010. However, in April, Russian President Vladimir Putin lifted the suspension after the nuclear framework deal between Iran and the P5+1 – U.S., U.K., France, Russia, China and Germany – was reached.

But the move by Moscow was strongly criticized by the United States and Israel, who fear that the missile defense system could make it more difficult to use the military option against Iran’s nuclear program.

Nevertheless, in an interview in April, President Barack Obama said that the U.S. could “penetrate” Iran’s air defense system, even with the S-300 in place.

“Even if they’ve got some air defense systems, if we had to, we could penetrate them,” Obama told MSNBC’s Chris Matthews.