European Union leaders urged U.S. President Donald Trump on Tuesday to safeguard their security interests ahead of his high-stakes summit with Russian President Vladimir Putin later this week, focused on the ongoing war in Ukraine.

The Europeans are eager to assert influence over the Friday meeting, from which they have largely been excluded. It remains uncertain whether Ukraine will even participate. Trump has said he wants to assess if Putin is serious about ending the conflict, now entering its fourth year.

However, Trump has unsettled U.S. allies by suggesting Ukraine may need to concede some Russian-held territory. He also indicated that Russia must agree to land swaps, though details of what Putin might be expected to give up remain unclear.

The Europeans and Ukraine are wary that Putin, who has waged the biggest land war in Europe since 1945 and used Russia’s energy might to try to cow the EU, might secure favorable concessions and set the outlines of a peace deal without them.

The overarching fear for European countries is that Putin will set his sights on one of them next if he wins in Ukraine.