U.S. President Donald Trump says Iran’s downing of a U.S. military surveillance drone with a surface-to-air missile on Thursday was a “big mistake,” but quickly added it may not have been intentional.

Trump made the remarks to reporters ahead of a meeting with Canadian Prime Minister Justin Trudeau in the Oval Office.

Trump said it’s "hard to believe" the move was intentional, saying it could have been carried out by someone who was acting “loose and stupid.”

He added that if the aircraft had been piloted, it would have made a “big, big difference.”

According to the New York Times, Trump had approved military strikes against Iran in retaliation, but apparently called off the operation in its early stages. 

The paper noted that it was unclear why the operation was called off or if future strikes were being considered.

Tehran has claimed responsibility for shooting down the unmanned U.S. surveillance drone, arguing that it illegally breached Iranian airspace near the Strait of Hormuz. The U.S. said the drone was in international waters when it was hit.

Asked how Washington will respond going forward, Trump told reporters they will soon find out.