KYIV, Ukraine — Ukraine has said it expects rapid progress on the security guarantees its allies could provide in a peace deal with Russia, but that one of the possible summit sites being pursued by the United States would be “challenging.”

Ukrainian President Volodymyr Zelenskyy urged swift progress Wednesday as military officials from the U.S. and Europe meet. Ukraine wanted to “have an understanding of the security guarantees architecture within seven to 10 days,” Zelenskyy told reporters in Kyiv.

Trump promised European leaders that the U.S. would help provide security guarantees in any settlement with Russia, a key concern for Kyiv. He has since made clear that this would not include U.S. troops on the ground, but might involve air support.

Once Kyiv has more clarity on what protections its allies are willing to offer, Zelenskyy said, he would then be ready to meet with Russia’s Vladimir Putin.

Where those talks might place has emerged as a possible stumbling block.

The White House has pressed ahead with making arrangements despite some public reticence from the Kremlin. Hungarian capital Budapest and the Swiss city of Geneva were among the sites being discussed, a senior administration official told NBC News, as Washington sought to secure a location and date.

But Zelenskyy said Wednesday that Budapest would be a “challenging” venue for his first direct talks with his Russian counterpart since the Kremlin launched its full-scale invasion.

The meeting should take place in a neutral European country, he said.

“I am not saying that Orbán’s policy was against Ukraine, but it was against supporting Ukraine,” Zelenskyy told reporters, referring to the Hungarian Prime Minister Viktor Orbán. “Switzerland, Austria — we agree,” he said, adding that Ukraine would also accept Turkey.

Russia on Wednesday signaled it was in no hurry for Putin and Zelenskyy to sit down together.

When it comes to meetings at the “highest level,” Foreign Minister Sergey Lavrov said, “they must be prepared with the utmost care.”

Daryna Mayer reported from Kyiv, and Mithil Aggarwal reported from Hong Kong.