Rubio designates Iran over wrongful detentions, urges Americans to leave country 'immediately'

"The Iranian regime must stop taking hostages and release all Americans unjustly detained in Iran, steps that could end this designation and associated actions. We encourage it to do so," Rubio wrote. "No American should travel to Iran for any reason. We reiterate our call for Americans who are currently in Iran to leave immediately."

Rubio's comments came amid rising tensions between the U.S. and Iran as they take part in indirect nuclear negotiations. 

When asked how close a decision may be, Trump told a reporter, "I'd rather not tell you, you would have the greatest scoop in history, right?"

"I guess you could say there's always a risk," Trump said. "You know, when there's war, there's a risk in anything both good and bad."

This is a developing story. Please check back for updates.

Fox News' Efrat Lachter, Peter Doocy and Morgan Phillips, along with Fox News Digital's Rachel Wolf contributed to this report.