Russian President Vladimir Putin must meet with Ukrainian President Volodymyr Zelenskyy before he can secure a bilateral with President Donald Trump, a White House official said Thursday.

The new precondition outlined by the White House comes after Trump told European leaders he intends to meet with Putin in person, followed by a trilateral with the leaders of Russia and Ukraine. Trump told reporters late Wednesday that while there was a “really good prospect” of a meeting taking place, he wouldn’t classify it as a “breakthrough.”

The official was granted anonymity to share private conversations around the potential meetings.

Trump’s continued engagement suggests he still sees a window to end the conflict through diplomacy, though the new parameters could complicate Putin’s interest in the talks. The Russian president has so far resisted meeting with Zelenskyy, as it legitimizes him as the leader of Ukraine.

It also remains unclear what any of the potential meetings mean for Trump’s Friday deadline for imposing additional sanctions against countries that purchase Russian energy. The U.S. president has threatened to take that action to punish Moscow if Putin doesn’t take steps toward ending the war in Ukraine. Trump has grown increasingly angered at Russia’s role in prolonging the conflict and stymieing peace talks, as Moscow continues airstrikes on civilian targets in Ukraine.

Trump’s envoy to the Middle East, Steve Witkoff, has held at least five meetings with Putin since February but all of the contact has failed to deliver any breakthroughs. Trump has grown increasingly frustrated with Putin, who has dramatically escalated Russia’s attacks on Ukraine since the diplomacy began.

At various points along the way, American officials have expressed they were close to some sort of agreement that would essentially freeze the conflict on its current lines and Witkoff’s team hopes Russia will eventually be open to such concessions again, a person familiar with the matter said.

Putin adviser Yuri Ushakov said before the White House’s condition was known that he expects a Trump-Putin summit as early as next week but the requirement makes that less likely. Ushakov played down the likelihood that Zelenskyy would join the meeting.

Putin blew off a possible meeting with Zelenskyy in Istanbul in May after Trump had set one of his many deadlines for Russia to make progress toward peace. Russian officials said at the time that Putin would only see Zelenskyy after a draft settlement was reached, while the Trump administration has repeatedly emphasized the importance of the two leaders speaking with each other.