European leaders, eyeing crucial gaps in their countries¡¯ defense capabilities, are still holding out hope that Donald Trump will make good on his offer to give Ukraine concrete security guarantees, even as a negotiated peace looks increasingly improbable.

Europe has critical shortfalls in space-based intelligence and surveillance, and integrated air and missile defense ¡ª the primary areas that the U.K.¡ª and French-led coalition of the willing hopes U.S. assistance will cover. It would cost Europe $1 trillion to replace conventional U.S. military capabilities assigned to the region, according to an International Institute for Strategic Studies report published last week.

The U.S. provides most of NATO¡¯s intelligence, surveillance and reconnaissance, including satellites, which has proved critical in the response to Vladimir Putin¡¯s invasion of Ukraine. Replacing that would cost Europe $4.8 billion, according to the report, ¡°Progress and Shortfalls in Europe¡¯s Defense.¡± European officials say the U.S. must continue to provide that under a peace deal, so Ukrainian and European forces can be alerted to any Russian breach.