HANOI/WASHINGTON, D.C. — The United States and Vietnam are discussing the sale of Lockheed Martin C-130 Hercules military transport planes to Hanoi, two people familiar with the discussions said, in a sign of closer security cooperation between the two former foes.

The talks could lead to a supply agreement this year, the sources said, in what would represent Vietnam's largest military deal since it said publicly at the end of 2022 that it intended to diversify its defense supplies, which have for decades relied heavily on Russian gear.