President Biden is welcoming more than three dozen world leaders to Washington, D.C., this evening as the annual NATO summit gets underway, marking the 75th anniversary of the nuclear-armed military alliance. Ahead of the talks, NATO’s outgoing Secretary General Jens Stoltenberg said allies were finalizing language stating that Ukraine is on an “irreversible” path to NATO membership.

The NATO summit is opening after Russian President Vladimir Putin welcomed Indian President Narendra Modi to Moscow for formal talks.

This comes as more than 700 members of the Union of Concerned Scientists signed an open letter to President Biden urging cancellation of the Air Force’s Sentinel weapon system, a new generation of intercontinental ballistic missiles that’s expected to cost more than $130 billion. In a statement, the Union said, “These weapons — stored in silos across the Plains states — place a target on communities and increase the risk of nuclear war while offering no meaningful security benefits.”