U.S. President Donald Trump on Friday said he called off a planned military strike against Iran because it would have been a disproportionate response to Tehran's downing of an unmanned U.S. surveillance drone, adding that more sanctions have been imposed. 

"We were cocked & loaded to retaliate last night on 3 different sights (sic) when I asked, how many will die," Trump wrote in a series of morning tweets. "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."

Trump said U.S. sanctions imposed on Iran were having an effect and, without mentioning details, said more were added Thursday night. 

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What comes next as tensions mount high between U.S., Iran?

Iranian officials told Reuters on Friday that Tehran had received a message from Trump warning that a U.S. attack on Iran was imminent but that he was against war and wanted to talk. 

Trump's tweets did not address whether he had sent a message to Iran's leaders but repeated his attacks on the deal secured by his Democratic predecessor, Barack Obama. He also reiterated his stance that Iran would not be allowed to obtain nuclear weapons. 

The escalating tensions come after Tehran on Thursday said it had shot down an unmanned U.S. military surveillance drone with a surface-to-air missile following a spate of attacks on oil tankers in the Gulf region.