President Donald Trump will speak by phone with Russian President Vladimir Putin on Thursday, a White House official said.

The call comes a day before Trump is scheduled to meet with Ukrainian President Volodymyr Zelenskyy at the White House.

The official, granted anonymity to disclose the call, did not provide any further details.

Trump told Zelenskyy over the weekend that he may give the Russian leader an ultimatum: Get serious about peace talks or the U.S. would send Ukraine long-range Tomahawk missiles in its increasing offensive against Russia.

Trump, speaking to reporters aboard Air Force One on Saturday, said he might speak to Putin about the decision first, calling it a potential “big step” in the war.

“I might have to speak to Russia, to be honest with you, about Tomahawks. Do they want to have Tomahawks going in their direction? I don’t think so,” Trump said. “I think I might speak to Russia about that, in all fairness. I told that to President Zelenskyy, because Tomahawks are a new step of aggression.”