President Donald Trump said he was in "no hurry" to attack Iran, the morning after after he called off missile strikes against the country with 10 minutes to spare.

In a series of tweets Friday, the president said he called off the strike because he believed the attack would have been disproportionate to Iran's downing of an unmanned American surveillance drone.

"We were cocked & loaded to retaliate last night on 3 different sights when I asked, how many will die," Trump wrote. "150 people, sir, was the answer from a General. 10 minutes before the strike I stopped it, not [...] proportionate to shooting down an unmanned drone. I am in no hurry, our Military is rebuilt, new, and ready to go, by far the best in the world."

Trump also said he preferred to move forward with economic pressure.

"Sanctions are biting & more added last night," Trump said. "Iran can NEVER have Nuclear Weapons, not against the USA, and not against the WORLD!"

The Treasury Department has not announced new sanctions, and a spokesperson did not immediately respond to a request for comment. Treasury Secretary Steve Mnuchin was scheduled to deliver remarks in Florida on Friday morning.

The White House and Department of Defense did not immediately respond to a request for comment.

Trump on Thursday approved military strikes on Iran before calling them off. Officials were still expecting the operation to move forward at 7 p.m., reports said. The New York Times, which first reported on the president's approval of the strikes, wrote that Trump had approved attacks on Iranian targets like radar and missile batteries.

The U.S. and Iran have disputed the location of an American drone downed by an Iranian surface-to-air missile Thursday. The U.S. claims the drone, an RQ-4A Global Hawk worth more than $100 million, was flying over international waters. Iran claims that it was flying over its territory.

-- CNBC's Jacob Pramuk contributed to this report.