Zelensky finds himself in the unenviable position of having to stand his ground in the face of an increasingly impatient Donald Trump, who appears to have been swayed by Putin and who has already accused Zelensky of standing in the way of peace.
Trump will probably tell Zelensky he must agree to give up land. This will be extraordinarily difficult for the Ukrainian president to give in to as it would entail retreating from Donetsk and Luhansk, regions which thousands of Ukrainian soldiers have fought and died to protect since 2022.
It would also allow Russia to end up in control of huge swathes of territory it could later use as a launchpad for further aggression.
So Zelensky cannot agree to land concessions without strong security guarantees that would kick in should Russia attack again. Those could have been provided by Nato, but Trump has made it clear Ukraine will not join the alliance.
Details of any alternative guarantees have likely not been worked out yet, but without them it will be difficult for Zelensky to make any commitments.
Ukraine is also concerned by the fact that Trump seems to have moved on from wanting a ceasefire to pushing for a full peace deal. This could take an exceptionally long time, allowing in the meantime for continued Russian attacks, civilian deaths and frontline losses.