The European Union’s top diplomat on Thursday ramped up pressure on Ukraine’s international backers to lift restrictions on the use of weapons they provide to the conflict-ravaged country to allow its armed forces to strike targets inside Russia.

The U.S. restricts the use of long-range ballistic missiles it provides to Ukraine and some EU members also limit the use of their weapons. Ukraine is desperate to target airfields and other military installations inside Russia that are used to stage attacks on its armed forces and civilians.