Russia on Tuesday rejected President Donald Trump’s demand for a ceasefire deal to end the war in Ukraine within 50 days, calling it “unacceptable” and insisting its military campaign will continue until its goals are met.

Responding to Trump’s threat to impose sweeping secondary tariffs on countries that continue doing business with Moscow if no deal is reached, Deputy Foreign Minister Sergey Ryabkov urged a focus on diplomacy, while warning Russia’s objectives remain non-negotiable.

“Any attempts to make demands, especially ultimatums, are unacceptable to us,” Ryabkov said, according to state-run TASS. “We need to focus on political and diplomatic work. The President of the Russian Federation has repeatedly said that we are ready to negotiate and the diplomatic path is preferable for us. But if we cannot achieve our goals through diplomacy, then the [special military operation] will continue. This is an unshakable position.”

He called on Washington and NATO to take that position “with the utmost seriousness.”

Kremlin spokesman Dmitry Peskov described Trump’s remarks as “quite serious,” saying the Kremlin needed time to analyze them.

“If and when President Putin deems it necessary, he will definitely comment,” Peskov said.

Former Russian President Dmitry Medvedev dismissed Trump’s words as “a theatrical ultimatum,” adding in a social media post that “Russia didn’t care.”

The pushback followed Trump’s Monday comments in the Oval Office alongside NATO Secretary General Mark Rutte. Trump said his administration was “very unhappy” with Russia, and announced a new U.S. weapons sale to NATO allies, who would in turn send the arms to Ukraine.

“We’re not buying it, but we will manufacture it, and they’re going to be paying for it,” Trump said. Rutte praised the arrangement as “logical,” adding that it ensures Ukraine has the means to defend itself.

Trump also expressed frustration with Putin, calling him “absolutely crazy” for targeting Ukrainian civilians and describing their past phone conversations as meaningless.

“I always hang up, say, ‘Well, that was a nice phone call.’ And then missiles are launched into Kyiv or some other city and I say, ‘That’s strange,’” Trump said. “After that happens three or four times, you say, the talk doesn’t mean anything.”

Asked if he was finished trying to deal with the Russian leader, Trump replied: “I’m not done with him. But I’m disappointed in him.”

Russia’s full-scale invasion of Ukraine began on February 24, 2022, following its annexation of Crimea and years of support for separatists in eastern Ukraine. Moscow still holds Crimea and large parts of eastern Ukraine, though its claim to those territories is not recognized by the U.S., the U.N., or most of the international community.

One of Russia’s key conditions for a ceasefire remains the recognition of at least some of its occupied territory as Russian.