The State Department can't rule out the possibility that last year's nuclear agreement has emboldened Iran into becoming more confrontational with the United States.

"I can't rule that out," department spokesman Mark Toner said when asked on Tuesday. "Iran, like many countries, has an internal political process that's defined by a lot of different dynamics, but I can't give an assessment in that regard one way or the other."

Toner admitted the U.S. has seen some "disturbing" trends with Iran, such as increased harassment of U.S. military assets in the region. But Toner said that makes the nuclear agreement all the more valuable, since Iran is at least not able to become more aggressive at the same time that it pursues nuclear weapons.

"In our view, it only makes the significance of the nuclear agreement that much more important, because the last thing anyone would want to see in the region is a nuclear-armed Iran," he said.

Iran reportedly bothered U.S. Navy ships five times in July, and over the weekend, Iran threatened to fire on two Navy aircraft. Toner said the latest threat was "concerning."

"They're concerning, obviously. They escalate tensions ... needlessly escalate tensions, frankly," he said. "We have conveyed our concerns to Iran. I know the DOD has ... conveyed its concerns. First and foremost, I'm doing it publicly."