Republican Richard Lugar, Indiana's longest-serving senator, has died at 87, ONA reports citing BBC.
His non-profit organisation, the Lugar Center, says he died of complications from chronic inflammatory demylinating polyneuropathy, an illness which attacks nerves.
Lugar served in the Senate from 1977-2013, after a shock loss in a primary to a Tea Party-backed candidate.
He was well known as an authoritative voice on US foreign policy.