Donbas
Russia demands to retain large parts of Ukraine – even parts that are not under its control.
The claim includes all of Donbas in the east, where Ukraine still defends just over a tenth of the area. There, along the cities of Sloviansk and Kramatorsk, one of the country's strongest defense lines has been established.
Russia demands that Ukraine withdraw from there before a ceasefire can be discussed.
Ukraine refuses to recognize occupied territory as Russian, but has said it would discuss a frozen front line provided that the country's security is guaranteed.
The US has reportedly proposed that the Ukrainian-controlled part of Donbas become a neutral economic zone, but to no avail.
Guarantees
Ukraine wants guarantees that peace will last.
Its allies in Europe promise guarantees and troop deployments, but American guarantees are seen as crucial to deterring Russia in the long term.
At last week's Munich Security Conference, Ukrainian President Volodymyr Zelenskyy said that the Americans have offered guarantees that will last for 15 years. Ukraine wants them to last for 20 - and to be clearly formulated.
According to media reports, there has been talk of solutions where European allies would intervene first if Ukraine is attacked, followed by the US if the attack becomes sustained. Russia has objected to any foreign military presence in Ukraine.
Nuclear power plant
Russia occupies Europe's largest nuclear power plant, located right next to the raging front, on the banks of the Dnipro River in the Ukrainian region of Zaporizhzhia.
The parties accuse each other of shelling that could cause a meltdown, and the UN atomic energy agency is sounding the alarm.
Ukraine lacks a large part of its energy supply. In the talks, the US has proposed entering into a shared stewardship, without a hearing.
The clock is ticking
Both countries are suffering heavy losses and are having difficulty finding recruits, especially Ukraine. Russia's limited advancement comes at a greater cost in lives.
The Trump administration in the US wants a solution by this summer, according to Ukraine's Zelenskyy, referring to the US mid-term elections this fall. But the US is also reportedly demanding that Ukraine hold elections first - in line with statements from Russian President Vladimir Putin that Zelenskyy does not have a mandate to conclude a peace agreement.
Sanction-ridden Russia has fueled an extensive war economy with oil. But the economy is slowing down and with stricter measures, not least from the US, oil revenues are falling faster.
Since Russia launched its major invasion of Ukraine in February 2022, hundreds of thousands of soldiers have died in combat.
Neither side transparently accounts for its own losses during the war, but various independent investigations are being conducted.
At least 177,400 Russian soldiers have died, according to an ongoing review by the exiled Russian Mediazona and the British BBC, in which each of these soldiers has been identified by name. Russia's real death toll is believed to be considerably higher.
The Ukrainian government recently said that at least 55,000 Ukrainian soldiers have been killed, while noting uncertainty about the figure. Independent estimates suggest that the number is at least a hundred thousand.
