Washington, April 17 (IANS): At least nine Guantanamo Bay detainees have been transferred to Saudi Arabia, cutting the number of inmates of the notorious US detention facility in Cuba to 80, the Pentagon has said.

The nine detainees include Tariq Ali Abdullah Ahmed Ba Odah, a Yemeni cleared for transfer by the US government in 2009 who had been on a hunger strike since 2007 in protest of his indefinite detention without charge or trial, said Pentagon on Saturday.

"The US is grateful to Saudi Arabia for its humanitarian gesture and willingness to support ongoing US effort to close the Guantanamo Bay detention facility," Xinhua news agency cited the Pentagon as saying.

The Saudis agreed to accept the detainees after "lengthy negotiations", marking a potential turning point in the US's often frayed relations with Saudi Arabia, a US official said.

The transfer also came ahead of a visit by US President Barack Obama to Riyadh next week to meet Gulf leaders to discuss the campaign against the extremist Islamic State group.

In his apparent last-ditch effort to seek cooperation from a hostile Republican-controlled Congress to close the Guantanamo detention facility, Obama unveiled a long-stalled closure plan in February.

According to the plan, some of the detainees still held in Guantanamo would be transferred to other countries, and the Obama administration would review the threat posed by detainees who were not eligible for transfers and identify those eligible for military trials.

However, the closure plan left unanswered a crucial question as to where the administration would put some detainees ineligible for transfers inside the US.

Republicans in the Congress had already pledged to fight against bringing any Guantanamo detainees back to the US.