Washington (CNN) President Barack Obama on Friday downplayed the significance of Russia's recent announcement that it would sell a missile-defense system to Iran, despite the White House having pressured Moscow since 2009 to refrain from making the transfer and having long seen limiting Tehran's military capacity as a key strategic objective.

The $800 million sale comes as the U.S. and world powers, including Russia, negotiate a deal to curb Iran's nuclear capabilities. Though the U.S. has stressed its preference for a diplomatic resolution to the issue, it has continued to warn that the military option remains a possibility should talks break down. Russia's sale would make any strike harder, which could affect how Iran calculates the risk of proceeding with its nuclear program.

"I'm frankly surprised that it held this long, given that they were not prohibited by sanctions from selling these defensive weapons," Obama said Friday at a news conference, referring to the six years that the Russians held off from moving forward with the deal at America's request.

But he said he felt the opposite when it came to why Russian President Vladimir Putin had now decided to proceed with it.

Read More