Iranian leader Ayatollah Ali Khamenei slammed U.S. sanctions on Saturday, calling them a “criminal act,” and said that Iran should strengthen its military to prevent war. 

“We should be strong to prevent any war against the country. Being weak will encourage our enemies to attack Iran,” Khamenei told Iranian air force commanders, with the comments being reported by state-run media. 

“Since the revolution their aim was to stop us from having a strong military and a strong air force ... but look at us now. We even build planes. We have transformed their pressure to opportunity,” he continued. Khamenei made the remarks as Iran celebrates 41 years since the Islamic revolution of 1979. 

Tensions between Tehran and Washington have been high since Iranian commander Qassem Soleimani was assassinated by a U.S. drone at Baghdad International Airport on Jan. 3. Soleimani's death has brought the U.S. to the brink of war with Iran, prompting the House on recently approve measures that reassert congressional authority over war powers.

President Donald Trump claimed that Soleimani was planning an “imminent” attack on U.S. assets in the Middle East region.

In retaliation, Iran shot missiles at U.S. military bases on Jan. 8. Although there were no casualties, some U.S. soldiers have experienced traumatic brain injury (TBI) since the attack.

If Iran decides to dramatically build up its military, it could increase tensions even further with the United States. Tehran has become increasingly hindered by U.S. sanctions, which have debilitated its economy.

"While Tehran may have temporarily pulled its punches, we should all be very worried about the new risks we will confront in a world where senior government officials are considered fair game," Brett Bruen, a former director of global engagement during the Obama administration, noted in an opinion article on Jan. 14.

The U.S. and Iran had experienced several diplomatic crises in 2019. 

In June, Iran shot down a U.S. drone operating in the Middle East region, angering the Trump administration. In September, a Saudi state-owned Aramco facility was attacked, cutting Saudi oil production temporarily. The U.S. and several European nations blamed Tehran for the attack. 

The sanctions against Iran began in November 2018 and were intended to force Iran to change its behavior in the Middle East region. Six months earlier, Trump announced the U.S. withdrawal from the Iran nuclear agreement. 

The Iran nuclear deal, known as the Joint Comprehensive Plan of Action (JCPOA), would remove sanctions on Iran in exchange for periodic international monitoring of its nuclear facilities. The deal was adopted in October 2015, during the Obama administration.