US President Donald Trump's senior envoys Steve Witkoff and Keith Kellogg will travel to Istanbul for potential talks on Thursday on how to end Russia's war in Ukraine, three sources familiar with the plans said on Tuesday.

However, a senior US official said it was unclear whether anyone from the Russian government would show up.

The White House, State Department, National Security Council and a spokesperson for Witkoff did not immediately respond to a request for comment.

President Volodymyr Zelenskiy will only attend the talks this week if Russia's Vladimir Putin is also there, an aide to the Ukrainian leader said on Tuesday, challenging the Kremlin to show it is genuine about seeking peace.

Moscow has not said whether Putin will travel to Turkey. Putin launched a full-scale invasion of Ukraine in February 2022, unleashing a war that has killed hundreds of thousands of soldiers on both sides.

When asked directly who would represent Russia at the talks, Kremlin spokesperson Dmitry Peskov said on Tuesday: "As soon as the president sees fit, we will announce it."

The senior US official said Washington did not expect an announcement about Moscow's plans until early Thursday morning.

Trump said on Monday he would fly to Istanbul for the meeting if necessary. He is in the Middle East region this week for meetings with officials from Saudi Arabia, the United Arab Emirates and Qatar.

US officials over the weekend had urged Zelenskiy to agree to meet Putin in person in Istanbul and to announce his plans publicly to openly show his intentions to negotiate with Moscow on a peace deal.

US officials are hoping Russia will agree to a comprehensive 30-day land, air, sea and critical infrastructure ceasefire, the senior US official said, adding that Kyiv has already agreed to abide by such a deal. The ceasefire is also backed by the Europeans, the official said.

If Russia does not agree to the ceasefire, the European Union has threatened to impose more sanctions on Moscow, the senior US official and another senior European official told Reuters. The sanctions package would target Russia's shadow fleet, the European official said.