By Olena Harmash and Vlad Smilianets

KYIV/DNIPRO, Ukraine (Reuters) -Mariupol natives Oleksandr and Liudmyla Lytvyn fled home three years ago during Russia's 86-day siege of the port city in southern Ukraine. Now they are following peace talks between the warring countries anxiously, fearing they may never return.

Mariupol, home to more than 400,000 people before the full-scale invasion, was seized by Russian forces in May 2022 when the city's last defenders were ordered to surrender, ending one of the bloodiest chapters of the war.

"We lived our entire life in Mariupol. I believe until the very last that it will be Ukrainian. I do not know how," Liudmyla, 65, a retired teacher, told Reuters.

Her longing to see occupied land back under Ukrainian control is widely shared, presenting a challenge to President Volodymyr Zelenskiy as he comes under pressure to consider territorial concessions under any peace agreement with Russia.

Ukraine has given no indication it is willing to do so, but Russian President Vladimir Putin has pushed Kyiv to cede not only occupied territory but also land not controlled by Moscow, while the United States has said loss of land seems inevitable.

More than three years into its full-scale invasion, Russia controls nearly one fifth of Ukraine and its troops are making incremental but steady gains in the east.

Zelenskiy himself has acknowledged that Ukraine cannot recapture all of its lost territory through military force, but wants to settle the issue through diplomacy.

Oleksandr, 65, said the issue of what Ukraine may have to give up in return for peace depends not only on Kyiv.

"The issue here is whether there are any limits on weapons," he said, referring to doubts over whether the U.S. will continue military support for Ukraine now that Donald Trump is in the White House and moving closer to Russia.

"It depends not only on Zelenskiy but also on other matters, weapons in particular," Oleksandr added, sitting next to his wife in a dormitory in the central city of Dnipro where they have moved temporarily.

Without U.S. military backing, Ukraine's position in negotiations would be significantly weakened.

RARE DIRECT TALKS

This month Kyiv and Moscow held their first direct talks since 2022, yielding little progress on ending the war.

After a subsequent phone call between Trump and Putin, the U.S. president appeared to withdraw from efforts to mediate peace, leaving Ukraine exposed against a larger enemy.

For displaced residents of Mariupol - the largest Ukrainian city to fall to the Russians since 2022 - that raises concerns not only about territorial concessions but also over whether justice will be served.

Vadym Boichenko, Mariupol's mayor-in-exile, said his team gathered evidence showing at least 22,000 civilians were killed in nearly three months of fighting that reduced a city once famous for its vibrant port and giant steel plants to rubble.

Human Rights Watch, along with Truth Hounds and SITU Research, estimated 8,000 people died from fighting or war-related causes, although it could not establish how many were civilians and said the true count may be significantly higher.

Reuters could not independently verify estimates of the death toll.

Russia pounded Mariupol with artillery, rockets and missiles and cut off access to electricity, heating, fresh water, food and medical supplies - creating a humanitarian catastrophe, Boichenko added.

"All we ask for is recognition (of the alleged crimes) and punishment," Boichenko said in Kyiv in one of the 'IMariupol' centres set up in 22 cities across Ukraine to help displaced residents with basic needs.

Russia's defence ministry did not respond to a request for comment on this article.

Russia says it liberated the city from Ukrainian "neo-Nazis", using one of the main justifications for its invasion that Kyiv and its allies dismiss as absurd.

Moscow-installed authorities have overseen a major reconstruction programme in Mariupol, and hold it up as a symbol of the benefits of Russia's annexation of four Ukrainian regions as well as the Crimean peninsula.

Russia blames Ukraine's armed forces for the city's destruction, alleging they used the local population as human shields. Ukraine rejects that accusation.

SWEEPING DEMANDS

Moscow has demanded that Ukraine withdraw its troops from four Ukrainian regions where fighting is raging, even though it does not control all of them.

The overwhelming majority of Ukrainians - 82% - reject those demands, according to an opinion poll by the Kyiv International Institute of Sociology conducted in May.

Slightly more than half of the population - 51% - would support a compromise with a de-facto recognition of currently occupied territories in exchange for robust security guarantees from Europe and the U.S., even though the latter has indicated it would not provide them.

But about 40% considered this unacceptable, raising questions over how Ukraine and Russia can break the deadlock in a nascent peace process.

"It is not fair to leave them what they took away. It is our land," said Dmytro, 35, who had settled in Mariupol after being forced to leave the eastern Ukrainian city of Donetsk in 2015.

Dmytro, now also based in Dnipro but concerned he might have to flee again, declined to give his last name as his mother and grandmother still live in the occupied Donetsk region.

"What we lived through in Mariupol is horror," he said, recollecting how he shielded his son, now 10, from bombardment and cooked food on open fires in the streets. He fled Mariupol in March 2022.

(Reporting by Olena Harmash and Vlad SmilianetsEditing by Mike Collett-White and Gareth Jones)