DUBAI, United Arab Emirates (AP) 鈥 U.S. negotiators worked on a proposed partial ceasefire in the 3-year-old war in Ukraine on Monday, meeting representatives from Russia one day after holding separate talks with a team from Kyiv.

It has been a struggle to reach even 鈥 which Moscow and Kyiv agreed to in principle last week -- with both sides continuing to attack each other with drones and missiles.

One major sticking point is what targets would be off-limits to strike, even after U.S. President Donald Trump spoke with the countries鈥 leaders, because the parties disagree.

While the White House said 鈥渆nergy and infrastructure鈥 would be covered, the Kremlin declared that the agreement referred more narrowly to 鈥渆nergy infrastructure.鈥 Ukrainian President Volodymyr Zelenskyy has said he would also like to see infrastructure like railways and ports protected.

Talks Monday in the Saudi capital of Riyadh were expected to address some of those differences, as well as a potential pause in to ensure the . Russian state media reported late Monday local time that the talks had ended.

In an exchange with reporters at the White House, Trump said territorial lines and the potential for U.S. ownership of a key nuclear power plant in southern Ukraine have been part of the talks.

Last week, Trump floated the idea of the U.S. taking control of the . The six-reactor facility 鈥 one of the world's largest 鈥 was seized by Russia early in the war.

鈥淪ome people are saying the United States should own the power plant 鈥 work it that way because we have the expertise鈥 to get the plant operating, Trump said. 鈥淪omething like that would be fine with me.鈥

Since falling under Russian control, the plant鈥檚 conditions have deteriorated. While its reactors have been shut down for years, they still require power and staff to maintain cooling systems and safety features. The facility is connected to Ukraine鈥檚 energy grid without producing electricity.

U.S. and Russian representatives met in the morning in Riyadh, Russia鈥檚 state Tass and RIA-Novosti news agencies reported. The U.S. and Ukrainian teams met Sunday.

Serhii Leshchenko, an adviser to the Ukrainian presidency, said the delegation remained in Riyadh on Monday and expected to meet again with the Americans. In his nightly address Monday, Zelenskyy said representatives from Ukraine and the U.S. will meet again, although he did not specify when.

Grigory Karasin, head of the foreign affairs committee in the Russian parliament鈥檚 upper house and a participant in Monday鈥檚 talks, told the Interfax news agency the negotiations were going on in a 鈥渃reative way" and that the U.S. and Russian delegations 鈥渦nderstand each other鈥檚 views.鈥

Meanwhile, both Russia and Ukraine continued to launch attacks across their borders.

The Russian Defense Ministry said Monday a Ukrainian drone attacked an oil pumping station in southern Russia that serves a pipeline carrying Kazakhstan鈥檚 Caspian Sea oil to the Russian port of Novorossiisk for export. It said the drone was downed before it could reach the pumping station.

Kremlin spokesman Dmitry Peskov said Monday the Russian military has been fulfilling President Vladimir Putin鈥檚 order to halt attacks on energy facilities for 30 days. He has accused Ukraine of derailing the partial ceasefire with attacks on Russia鈥檚 energy facilities, including a gas metering station in Sudzha in Russia鈥檚 Kursk region.

Ukraine鈥檚 military General Staff rejected Moscow鈥檚 accusations and blamed the Russian military for shelling the station, a claim Peskov called 鈥渁bsurd.鈥

Zelenskyy said Sunday evening that "since March 11, a proposal for an unconditional ceasefire has been on the table, and these attacks could have already stopped. But it is Russia that continues all this.鈥

He added that Ukraine's partners 鈥 鈥渢he U.S., Europe, and others around the world鈥 鈥 should increase pressure on Russia 鈥渢o stop this terror.鈥

Zelenskyy has emphasized that Ukraine is open to Trump's proposal of a full, 30-day ceasefire. Putin has made a complete ceasefire conditional on a halt of arms supplies to Kyiv and a suspension of Ukraine鈥檚 military mobilization 鈥 demands rejected by Kyiv and its Western allies.

Speaking on 鈥淔ox News Sunday,鈥 Trump鈥檚 special envoy Steve Witkoff said he expected 鈥渟ome real progress鈥 at talks and that a pause in hostilities by both countries in the Black Sea would 鈥渘aturally gravitate into a full-on shooting ceasefire.鈥

China rules out supplying peacekeeping forces

Asked about reports speculating that China might send peacekeepers to Ukraine to enforce any peace deal, Chinese Foreign Ministry spokesperson Guo Jiakun responded Monday with an unequivocal no.

鈥淟et me stress that the report is completely false. China鈥檚 position on the Ukraine crisis is clear and consistent,鈥 Guo said at a briefing.

China has provided Russia with trade earnings from oil and other natural resources, along with diplomatic backing, but has not given any weapons or sent any personnel. China is, however, on close terms with North Korea, which has sent troops to fight alongside the Russian army.

Ukrainian railways hit by cyberattack

A 鈥渕assive targeted cyberattack鈥 hit Ukrainian state railway operator Ukrzaliznytsia on Sunday, the company wrote on Telegram, adding that it was working to restore its systems on Monday. The company said the attack did not affect train movements or schedules but disrupted its online booking system.

鈥淭he railway continues to operate despite physical attacks on the infrastructure, and even the most vile cyberattacks cannot stop it,鈥 the company wrote.

Meanwhile, Ukraine's Special Operations Forces claimed Monday it destroyed four military helicopters in Russia's Belgorod region with the use of U.S.-supplied HIMARS rocket systems. It published drone footage on its Telegram page of what it said was the attack.

The strikes occurred at a concealed 鈥渏umping-off point鈥 for Russian aircraft used in surprise attacks on Ukrainian forces, the group said.

A Russian missile struck the northern city of Sumy, across the border from Russia's Kursk region, hitting residential buildings and a school, said regional head Volodymyr Artiukh. Children at the school were being evacuated at the time, and all were safe, he added.

But the regional prosecutor's office said 65 people were injured, including 14 children.

Earlier, Russia fired 99 attack and decoy drones into Ukraine overnight, according to Ukraine鈥檚 air force, of which 57 were shot down.

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Novikov reported from Kyiv, Ukraine. Associated Press writers Christopher Bodeen in Beijing and Aamer Madhani in Washington contributed.

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