NATO allies promised five long-range air-defense systems for Ukraine in a fresh show of support, even as leaders resisted offering the country a path toward membership and fresh assessments indicate the conflict with Russia is headed toward an indefinite stalemate.

The announcement was intended as a display of unity in the face of a stepped-up air barrage by President Vladimir Putin’s forces. It also drew attention to the challenge the allies have faced coming up with military aid: Tuesday’s promise repeated some commitments that had already been made in recent weeks.

In a speech to NATO leaders on Tuesday night, U.S. President Joe Biden called the air defense systems a "historic donation,” that would be accompanied by dozens of shorter-range systems and missiles. The U.S., Germany and Romania will each send a Patriot system, while a fourth will be cobbled together from parts from the Netherlands and others. Italy will send a SAMP-T system.