President Joe Biden and Vice President Kamala Harris spoke by phone with Griner, the official said, adding that she was in good spirits. The call included Griner's wife, Cherelle.

"She is safe. She is on a plane. She is on her way home," Biden said in a tweet.

Biden is to make remarks at 8:30am (14:30 CET), the White House said.

Griner a star of the Women's National Basketball Association's Phoenix Mercury, was arrested on February 17. Talks to secure her release were complicated by Russia's February 24 invasion of Ukraine and the subsequent deep souring of ties between Washington and Moscow.

A two-time Olympic gold medallist, Griner was arrested at a Moscow airport when vape cartridges containing cannabis oil, which is banned in Russia, were found in her luggage.

She was sentenced on August 4 to nine years in a penal colony on charges of possessing and smuggling drugs. She had pleaded guilty, but said she had made an "honest mistake" and had not meant to break the law.

Last month she was taken to a penal colony in the Russian region of Mordovia to serve her prison sentence.

The swap involved former arms dealer Viktor Bout, CNN reported.

Variously dubbed "the merchant of death" and "the sanctions buster" for his ability to get around arms embargoes, Bout, 55, was one of the world’s most wanted men before his arrest.

For almost two decades, Bout became the world’s most notorious arms dealer, selling weaponry to rogue states, rebel groups and murderous warlords in Africa, Asia and South America.

For experts on the Russian security services, Moscow's lasting interest in Bout hint strongly at Russian intelligence ties.