Various opposition leaders declined to publicly confirm the signing, saying there would be an announcement on Sunday, May 22.
One opposition official said on condition of anonymity that opposition leaders Saturday, May 21, met with the secretary general of the Gulf Cooperation Council, the bloc that is sponsoring the accord, along with the American, British, European Union and United Arab Emirates ambassadors.
But he did not confirm or deny that the accord had been signed, instead saying that 'the important thing is that the president sign' the agreement.
Saleh, who has been in power since 1978, has since January faced protests calling for his departure, in which at least 180 people have been killed, according to a toll compiled from reports by activists and medics.
A spokesman for Saleh's ruling General People''s Congress (GPC) said earlier in the day the president would sign on Sunday, May 22.
"The signing of the plan will be on Sunday in Sanaa," Tareq al-Shami said. "Saleh will sign the document in his capacity as president of the republic and the GPC." Under the terms of the deal, Saleh would hand power to the vice president 30 days after the agreement is signed, and he and his aides would be granted immunity from prosecution by parliament.
A national unity government led by a prime minister from the opposition would be formed, and a presidential election would follow 60 days after Saleh's departure.