President Donald Trump signed an executive order Monday placing “hard-hitting” sanctions on Iran after increased tensions over the past week.

The order imposes sanctions on the Supreme Leader of Iran, the Office of the Supreme Leader, and others, denying them “access to key financial resources.”

The move comes just days after Iran shot down an unmanned U.S. surveillance drone, an action the president called “not good and not appropriate.” (RELATED: Iran Downs U.S. Navy Drone)

“Today’s action follows a series of aggressive behaviors by the Iranian regime in recent weeks including shooting down of U.S. drones,” Trump explained during the signing in the Oval Office. “These measures represent a strong and proportionate response to Iran’s increasingly provocative actions.”

In addition to shooting down the U.S. drone, Iran has been blamed for an attack on two oil tankers in the Strait of Hormuz. Following the dissolution of the Iran Deal, Supreme Leader Ayatollah Ali Khamenei warned last week that the U.S. could not stop his country from developing nuclear weapons.

In response to Iran’s aggression, Trump was reportedly prepared to launch a military strike against the Middle Eastern country. However, shortly before giving the final order, the president said he pulled back after learning the strike would kill 150 people.

“Ten minutes before the strike I stopped it, not proportionate to shooting down an unmanned drone,” Trump tweeted Friday.

Trump reiterated during the signing of the new sanctions that the U.S. has shown “restraint” in regards to Iran, but warned that they could opt for a tougher response in the future.

“I think a lot of restraint has been shown by us – a lot of restraint – and that doesn’t mean we’re going to show it in the future,” Trump said.