Donald Trump is frustrated with Ukrainian leader Volodymyr Zelensky, and views him as the “bad guy” who is pushing the world closer to nuclear war, according to a report published by the New York Times this week.

Unnamed Trump advisers told the NYT that the US president “exasperated” with both Russian President Vladimir Putin and Zelensky, but “reserves special animosity” for the Ukrainian leader.

RT reports: Although Trump has said it is “understandable” that Ukraine wants to keep fighting, his stance toward Zelensky is notably harsher than toward Putin, the report says. The US president reportedly tends to be more deferential to his Russian counterpart, and previously believed that their “very, very good relationship” would help end the conflict. Because of this, he has thus far refrained from imposing new sanctions on Moscow.

On Wednesday, the two leaders held a 75-minute phone conversation in which Trump said they discussed Ukraine’s recent attack on Russian airbases that reportedly host strategic aircraft. “President Putin did say, and very strongly, that he will have to respond to the recent attack on the airfields,” Trump said.

The Kremlin confirmed the conversation. Russian presidential aide Yury Ushakov said Putin informed Trump of Ukraine’s efforts to derail peace talks between Moscow and Kiev, including “terrorist” attacks on civilian targets. Ushakov was apparently referring to incidents of railroad sabotage in the regions of Bryansk and Kursk in which seven people died and more than 100 were injured.

Following the call, Zelensky posted a statement on Telegram, saying: “If the world reacts weakly to Putin’s threats, then he perceives this as the world’s readiness to turn a blind eye to his actions… If the strong do not stop Putin, it means that they share responsibility with him.”

Trump previously engaged in a public spat with Zelensky when the two met at the White House in late February. At the time, the US president accused Zelensky of “gambling with World War III,” and of being “disrespectful” and ungrateful for American support.