FIRST OFF . . .

“Welcome Home,” a celebrity-studded concert/tribute dedicated to Vietnam War veterans, will be staged at RFK Stadium in Washington on the Fourth of July, actor Jon Voight announced Wednesday in New York. Neil Diamond, Linda Ronstadt, John Fogerty, the Four Tops and Crosby, Stills and Nash are among those slated to salute the vets in song. The concert will also feature mini-documentaries and appearances by Voight, John Ritter (both of whom have portrayed Vietnam vets in film roles), Peter Fonda, Ricardo Montalban and Oliver Stone, the Oscar-winning writer-director of “Platoon.” HBO will air the event, which is being organized by Welcome Home Inc., a nonprofit organization of celebrities from the entertainment industry who lend their support to Vietnam veterans.