President Donald Trump listens to questions from reporters during a meeting with Canada's Prime Minister Justin Trudeau in the Oval Office of the White House in Washington, U.S., June 20, 2019.

As tensions between the U.S. and Iran escalate, President Donald Trump approved military strikes on several Iranian targets — but abruptly pulled back from launching them on Thursday night, according to three U.S. officials who spoke on the condition of anonymity to discuss sensitive national security decisions.

The attacks were approved in retaliation to to Iran shooting down an unmanned American spy drone, and officials were still expecting the operation to go ahead as late as 7 p.m. ET. It was not clear why the strikes were called off.

The New York Times first reported on the aborted strike plan.

The Times report, published late Thursday, cited multiple senior administration officials involved in or briefed on the deliberations of the strikes.

Military planes and ships were getting ready to attack Iranian targets — such as radar and missile batteries — when the attack was called off, according to the Times. No missiles had been fired, said the report.

The Times said it wasn't clear whether Trump had simply changed his mind about attacking Iran, or the administration switched course due to logistics and strategic considerations. It also wasn't clear if the attacks would still go ahead, according to the report.

The Department of Defense did not return CNBC's requests for comment. A senior administration official said: "We do not comment on pre-operational military planning." The Times said that the White House and Pentagon officials declined to comment. No government officials asked the Times to withhold the article, the report said.

Trump on Twitter: Iran made a very big mistake!

Earlier on Thursday, Trump said on Twitter that "Iran made a very big mistake!" by shooting down the U.S. spy drone. Iran claimed that the aircraft was over its territory, but the U.S. Central Command said it was flying in international airspace.

On the same day, Trump also said at the White House: "I think they made a mistake, and I'm not just talking the country made a mistake. I think that someone under the command of that country made a big mistake."

Tensions between Washington and Tehran have been rising since the Trump administration's decision to withdraw from the 2015 Iran nuclear agreement.

Before the confrontation over the American drone, the U.S. accused Iran of recent attacks on oil tankers in the Persian Gulf region.

— CNBC's Eamon Javers contributed to this report.

For the full story on Trump pulling back military strikes on Iran, read The New York Times.