Under escalating pressure from U.S. sanctions, Iran's leaders face an existential crisis. As a result, they are increasingly likely to strike out against the U.S. in response.

The latest U.S. action against Iran came on Monday when Secretary of State Mike Pompeo ended waivers that allow foreign nations to purchase Iranian oil without U.S. sanction reprisals. Pompeo, however, also pledged that Saudi Arabia and the United Arab Emirates will increase their oil production to maintain price stability. It's the correct course of action.

Yes, the U.S. must ensure this doesn't harm America's growing partnership with India, a top importer of Iranian oil, and yes, the U.S. should more tightly define its demands of Iran. Trump should also authorize similar action against Nicolás Maduro's Venezuelan regime.

Still, ending waivers will reduce the power of Iran's hard-line faction. Their declining revenue means less ability to spread sectarian brutality. And for the fanatics, America's pressure comes at an inopportune time. Iran's economy is already suffering. Economic growth is lethargic, inflation reached 47% in March 2019, food inflation is even higher, and youth unemployment soars. With Iran highly dependent on oil exports for its foreign capital generation, U.S. oil export pressure will cut deep.

The hard-liners need oil sales to prop up the security agencies and militias that sustain its power. Crude oil prices are now at $65 a barrel and have been rising since January, when they went as low as $45 per barrel. Unable to sell oil at today's higher price, Iran is losing out at the margin on hundreds of millions of otherwise easy dollars.

Yet the U.S. shouldn't be arrogant here, for it is precisely the coming economic damage and lost opportunity that will motivate the hard-liners to escalate.

While that escalation has been coming for months now, the portent of a near-total end to oil export revenue will catalyze the hard-liners' fear and anger. They live and die for the Islamic revolution and will protect that interest at high cost. The most likely Iranian action is closing the Strait of Hormuz, through which vast oil supplies flow. Iran might hope that this action would induce international pressure on the U.S. to reduce its pressure on Iran.

Pompeo knows this, which explains why he warned on Monday that any violence by Iranian officers, agents, or militias will meet forceful retaliation. Regardless, choppy waters lie ahead.