Trump told NBC News he was “pissed off” after Putin reportedly said Russia would “finish off” Ukraine’s troops and that a UN-run transitional government should be installed that would remove President Zelensky from power, according to AFP. In response, Trump threatened to impose “secondary tariffs” of up to 50% on all countries that import Russian oil—a move that would likely cripple the country’s government revenue.

“If Russia and I are unable to make a deal on stopping the bloodshed in Ukraine, and if I think it was Russia’s fault—which it might not be—but if I think it was Russia’s fault, I am going to put secondary tariffs on oil, on all oil coming out of Russia,” he told NBC. 

It’s unclear whether Trump’s recent comments mark a change in tone on Russia given his previous comments praising Putin and recent U.S. policy actions, said Carnegie Mellon University public policy professor Sarah Mendelson. In February, the U.S. stunned allies in Europe when it twice sided with Russia in voting against a resolution drafted by European leaders condemning Russia’s actions and advocating for an independent Ukraine.

Yet, Putin’s suggestion that a UN-run transitional government be installed in Ukraine clearly has ulterior motives.

“Who knows how serious he is about a UN mandate, but he probably imagines that maybe he could manipulate a UN mandate. If it were a NATO peacekeeping force, he obviously wouldn’t accept that, but he also couldn’t manipulate it,” Mendelson told Fortune.

Still, one expert says Trump’s sudden rebuke of Putin shows he’s serious about striking a peace deal in the near term. 

Last month, Trump berated Zelensky in the Oval Office in part because he was reportedly pushing back against U.S. conditions for a peace deal. But Trump’s most recent comments about Putin and his threat of imposing secondary tariffs, a threat never wielded by the Biden administration, shows he is playing both sides and pressuring Putin to stop slow-walking a possible peace deal, said BCA Research chief strategist Marko Papic.

“Trump is basically saying, ‘I blew up at Zelensky in my office about this very same thing, I’m going to blow up at you [Putin] as well. I want peace right now,’” Papic told Fortune.

Trump’s secondary tariffs of up to 50% on Russian oil would essentially eliminate half of the country’s government revenue as companies, especially in India and China, look for other sources of crude, said Papic. 

While this move will raise oil prices internationally, as more countries and companies compete for the same non-sanctioned crude as before, Papic added that Trump is willing to allow a short-term price hike for oil above $100 per barrel, from its current $75.

“I think Trump can very comfortably cause a lot of geopolitical risks to rise—see oil prices go north of $100 in the interest of putting those geopolitical risks to bed permanently and then focus on getting more supply on the market,” Papic said. 

A forever war would not benefit the West or Ukraine, and ensuring Ukraine remains an independent state, even with vast areas of its territory ceded to Russia, is a U.S. priority, Papic said. 

Despite Putin’s ambition of conquering the entirety of Ukraine, and particularly the politically significant Donbas region, he is likely to cave and agree to a peace deal given Trump’s serious threats, he added.

“My view here is that Putin will have to back down and accept the borders as they are, which is already as good of a deal as he’s ever going to get,” Papic said. “I think that he’s starting to realize very, very clearly how focused Trump is on the deadline and the timeline—he really wants this over right now.”