text:  Biden's performance is under scrutiny, though, as he hosts more than 30 heads of state in Washington. Ukraine's fight with Russia remains front and center at the summit. Secretary of State Antony Blinken says NATO is sending F-16s to Ukraine, part of a package that he says will be key to defending Ukraine's infrastructure. Here's NPR's Michelle Kellerman. At a public forum on the sidelines of the 75th anniversary NATO summit, Secretary Blinken was asked to give more details about the alliance's plans to beef up Ukraine's air defenses.