What are the concerns regarding the U.S.-Russia talks in Saudi Arabia about the Ukraine conflict?

Many Europeans fear that Vladimir Putin will negotiate a deal with President Trump that rewards Russia with Ukrainian territory. For nearly three years, Russia has been isolated from the West through sanctions after Putin's invasion of Ukraine, but recent developments—including a phone call between Trump and Putin and the current talks—are viewed by some as already representing a victory for Putin. The primary concern is that any potential agreement might not provide Ukraine with necessary security guarantees, potentially allowing Putin to reinvade Ukraine in the future. This situation is especially worrying as the talks are taking place without Ukrainian representatives present, raising questions about whose interests are being prioritized in these negotiations.