The United States will hold separate talks with Russia and Ukraine in Saudi Arabia to iron out details of a possible limited cease-fire in what could be a crucial step toward a full cessation of hostilities in the war.

Russia and Ukraine both agreed this past week to temporarily halt strikes on energy infrastructure, but how and when to implement that partial truce are questions that have yet to be decided as attacks persist.

The talks — to be held in Riyadh, the Saudi capital, with American representatives mediating — are expected to focus on hammering out those details and on safety for shipping in the Black Sea. Kyiv’s delegation will first meet with U.S. mediators on Sunday, a Ukrainian official said, followed by Moscow-Washington talks on Monday.

The Ukrainian official, speaking on condition of anonymity to discuss a sensitive matter, said Sunday’s talks would begin in the evening, Kyiv time. He added that the Ukrainian delegation might hold additional discussions with U.S. officials on Monday, depending on progress.

Steve Witkoff, whom President Trump has tapped to be his personal envoy to President Vladimir V. Putin of Russia, has said that the ultimate goal of the talks is a 30-day full cease-fire that would allow time for negotiations on a permanent truce.

But the path toward such a truce has been shaky. Moscow continues to insist on maximalist positions, including about asserting territorial control and ensuring Ukraine never joins NATO. The Ukrainian government has repeatedly said that it will not concede to the Kremlin’s demands and accused President Vladimir V. Putin of Russia of stalling for time.

Unlike previous cease-fire discussions, which involved top government officials from all sides, this new round will focus on technical matters and will mostly involve diplomats and government advisers. Keith Kellogg, the U.S. special envoy to Ukraine, said that the American delegation would include some of his own staff, along with Michael Anton, policy planning director at the State Department; and aides to the national security adviser, Michael Waltz.

The Russian delegation

Dmitri S. Peskov, the Kremlin’s spokesman, said on Friday that Mr. Putin had personally selected negotiators for the talks. The Russian delegation will be led by Grigory B. Karasin, a senior Russian diplomat and lawmaker; and Sergey O. Beseda, an adviser to the head of the Federal Security Service, or F.S.B., the country’s domestic intelligence agency.

While Mr. Karasin has been involved in sensitive foreign policy talks before, Mr. Beseda’s choice came as a surprise to some.

An influential spymaster, Mr. Beseda was head of the F.S.B. department responsible for international intelligence operations. He has been described by Russian news outlets as one of the main sources of intelligence that convinced Mr. Putin in 2022 that there was pro-Russian sentiment in Ukraine and that a brisk invasion could easily dismantle the government in Kyiv.

In 2023, Kyrylo Budanov, the head of Ukraine’s military intelligence, called Mr. Beseda a “very problematic person” for Ukraine who “has done a lot of evil.”

The Ukrainian delegation

President Volodymyr Zelensky of Ukraine said his defense minister, Rustem Umerov, would attend the negotiations in Riyadh. Mr. Umerov will be joined by Pavlo Palisa, a top military adviser to Mr. Zelensky, according to the Ukrainian official.

Both Mr. Umerov and Mr. Palisa are members of the Ukrainian delegation for peace talks that Mr. Zelensky appointed this month, a group led by his chief of staff, Andriy Yermak. Mr. Umerov was a key negotiator for Ukraine in peace talks with Russian diplomats in the early months of the war.

Given the technical nature of the talks on energy and shipping, Mr. Zelensky said that Ukraine would also send experts to Saudi Arabia. “There will be military, energy specialists, as well as people who are well versed in port and other civilian infrastructure,” he said on Wednesday.

Mr. Zelensky said Ukraine would prepare a list of infrastructure objects that could be included in the cease-fire agreement. He added that a third party would have to monitor the cease-fire, and suggested that the United States could do so.

While Russia and Ukraine may find common ground in talks about energy and shipping, both have laid out conditions for a complete cessation of hostilities that appear irreconcilable — a sign of the steep challenges ahead in any broader peace negotiations.

Moscow’s position

This past week, during a telephone conversation with President Trump, Mr. Putin said that Russia would agree to a temporary truce only if Ukraine stopped mobilizing soldiers, training troops or importing weapons for the duration of any pause in fighting.

Mr. Putin also demanded the complete halt of foreign military aid and intelligence to Kyiv, calling it “the key condition for preventing an escalation of the conflict and making progress toward its resolution through political and diplomatic means,” according to the Kremlin’s readout of the call.

The White House said that military aid and intelligence sharing to Ukraine would continue despite the Kremlin’s demands. But the Trump administration has been less clear on Moscow’s calls for territorial concessions and at times even appeared to align with the Kremlin’s stance.

Mr. Witkoff echoed a Kremlin talking point on Friday in saying that an “overwhelming majority” of Ukrainians living in four regions of the country that Russia has annexed had “indicated that they want to be under Russian rule” during referendums organized by Moscow. Those referendums were widely denounced as fraudulent and illegal by the international community.

Fundamentally, Russia’s position regarding the conflict has remained the same. The Kremlin says it wants to “eliminate the root causes of the crisis” — essentially demanding that Ukraine capitulate. That would mean Kyiv’s recognizing Russia’s territorial gains, declaring neutrality and agreeing to shrink its military, which would most likely leave Ukraine vulnerable to another invasion.

Kyiv’s position

Ukraine had previously agreed to an unconditional 30-day truce to cease all combat operations, at the urging of the Trump administration. But after Moscow said that it would support only a partial cease-fire on energy infrastructure, Mr. Zelensky spoke with Mr. Trump and agreed to the limited truce.

In recent days, Ukrainian officials have set out red lines going into negotiations: Kyiv will never accept Russian sovereignty over occupied Ukrainian territory, it will not agree to be blocked from joining NATO or to reduce the size of its army, and it must have security guarantees as part of any peace settlement.

Many Ukrainian officials and analysts express doubt that even a limited cease-fire will hold for long, noting that previous truces between Moscow and Kyiv were routinely violated, with each side blaming the other.

“I do not believe in a cease-fire. We’ve been through this before,” Kostyantyn Yeliseev, a seasoned diplomat and former Ukrainian deputy foreign minister who took part in cease-fire negotiations in 2014 and 2015, said in an interview.

What’s next?

Mr. Witkoff said on Wednesday in an interview with Bloomberg News that Mr. Trump and Mr. Putin were “likely” to meet in Saudi Arabia within weeks. American officials will also probably continue meeting their Russian and Ukrainian counterparts in the Middle East to discuss details of a possible limited truce.

But the foundations of the diplomatic process have been wobbly, analysts said, with Moscow and Kyiv ready to continue fighting.

“Both sides still believe that they can continue the war regardless of the American position,” said Dmitry Kuznets, a military analyst with the Russian news outlet Meduza, which operates from Latvia after being outlawed by the Kremlin.

He added, “Moscow’s and Kyiv’s visions of what an agreement could look like are still infinitely far from each other.”

Maria Varenikova contributed reporting