Josh Fattal and Shane Bauer, both 29, were flown into Muscat on an Omani Royal Air Force plane Wednesday after the Gulf sultanate of Oman paid their $1 million bail to get them released from Tehran's notorious Evin prison. Their case had poisoned already tense ties between Tehran and Washington.

Obama called Sultan Qaboos bin Said "to convey the United States' deepest appreciation for the Sultan's exceptional and successful role in securing the release of the young American hikers from Iranian detention and the cooperation between our governments in this endeavor," the White House said.

"The president expressed our gratitude to the sultan and his special envoy, Salim al-Ismaili, for sparing no effort to secure the release of Sarah Shourd last year, and Shane Bauer and Josh Fattal this past Wednesday, thus ending a painful chapter for the hikers and their families."

Shourd, Bauer's fiancee, was released last year on $500,000 bail also paid by Oman.

During their call, Obama and Sultan Qaboos "affirmed that the friendship and partnership between our two nations, as manifested in our cooperation for the release of the hikers, have only grown stronger, and that the United States and Oman will continue to work together on a broad range of common interests," the White House added in its statement.

Bauer and Fattal were arrested along with Shourd near the mountainous border with Iraq on July 31, 2009. All three have consistently maintained they innocently strayed into Iran while hiking in Iraq's Kurdistan region.

On August 21, Bauer and Fattal were each sentenced to eight years in prison by a revolutionary court in Tehran on charges of espionage and illegal entry. They appealed against the ruling.

Their arrests angered Washington, which already has deep differences with Tehran over its controversial nuclear program, its refusal to recognize Israel and its support for militant groups in the Middle East.

Copyright AFP (Agence France-Presse), 2011