On Sunday, Russian aluminum king and billionaire Oleg Deripaska posted his thoughts on social media and instant messaging site Telegram, accusing U.S. President Joe Biden of further fueling tensions after a Saturday speech in Poland in which Biden delivered scathing attacks against Russian President Vladimir Putin. 

Speaking from Warsaw—where the President spent two days meeting Ukrainian refugees, U.S. troops, and government officials—Biden said that Putin “should not remain in power.” Earlier on Saturday, Biden referred to Putin as a “butcher” and a “war criminal.”

The U.S. Secretary of State Antony Blinken soon clarified Biden’s comments, stating that the U.S. was not interested in “regime change in Moscow,” but the President’s statements provoked a heated response from the Kremlin nonetheless. 

A government spokesperson shortly declared that the choice of who could lead Russia was “not for Biden to decide,” while Dmitry Rogozin, the head of Russia’s space agency who has been particularly outspoken against the West, mockingly suggested on Twitter that the clarification had come from Biden’s medical care unit, appearing to call the president’s health into question.

In his Telegram post, Deripaska wrote that Biden’s comments were deepening differences and escalating tensions between Russia and the West, saying that there is now “some kind of hellish ideological mobilization underway on all sides.”

Deripaska wrote that the war could have ended “three weeks ago through reasonable negotiation,” but now appears unconvinced that the conflict will be resolved anytime soon, writing that “these people are preparing to fight for a few years more.”

The oligarch has been critical of Russia’s invasion, as well as the effect it would have on the country’s economy and citizens. Earlier in March, he made an urgent call for peace, predicting that a prolonged war could create a new ideological and economic barrier between Russia and the West, condemning his country to a “severe economic crisis” lasting at least three years.

Deripaska has been one of the few Russian oligarchs to object against the war over the past month, although he has been careful not to directly criticize Putin himself. Despite his recent comments criticizing the war, Deripaska has held close ties to Putin in the past. In a letter sent to Deripaska’s lawyers in 2020, the U.S. Treasury accused the oligarch of “holding assets and laundering funds on behalf of Russian President Vladimir Putin.”

The billionaire, who is currently worth over $2 billion according to Forbes, made his fortune under former Russian President Boris Yeltsin through the metal-making and mining industries in the 1990s. 

Deripaska was hit with a round of sanctions in the immediate weeks following the invasion, although he has also been under a different set of U.S. sanctions since 2018, when the U.S. Treasury accused him of money laundering, extortion, and wiretapping government officials.