Malaysian opposition leader Anwar Ibrahim said Sunday he was prepared to go to jail as he geared up for last-ditch rallies on the eve of a trial verdict that threatens his political career.

Anwar, 64, has toured the country in the past week, whipping up crowds of supporters with fiery speeches denouncing sodomy charges against him as a government frame-up aimed at neutralising him politically.

He was due to address supporters at his Kuala Lumpur home Sunday night, followed by a pair of separate rallies ahead of the following morning's highly anticipated verdict announcement.

In a brief interview at his home Sunday, Anwar told AFP he had prepared himself mentally for a guilty verdict on charges he sodomised a male aide in 2008.

Sodomy is illegal in Muslim-majority Malaysia and punishable by 20 years in jail. "Mentally, I am okay. I am psychologically prepared (for a guilty verdict)," said Anwar, who like many observers believes a guilty verdict is assured.

"Physically, of course, I am 64... my health conditions are, of course, not as great as when I was at the age of 50."

Kuala Lumpur was bracing for potential unrest, with the opposition saying it plans to gather 100,000 people outside the court on Monday where judge Mohamad Zabidin Diah will pronounce Anwar's fate.

But Anwar said his supporters were being urged to assemble peacefully and disperse quickly after the verdict. There have been no reports of unrest during his tour.

"I do not anticipate any violence tomorrow," said Anwar, who added that voters should take any revenge at the ballot box. Prime Minister Najib Razak must call the next elections by early 2012.

In a concession rare for a country where dissent is tightly controlled, police said they would allow the courthouse gathering, provided that it did not get out of hand.

In July, a rally for electoral reform by tens of thousands in the capital was crushed by police using tear gas and water cannon. About 1,600 people were arrested.

The verdict announcement has kindled memories of Anwar's stunning fall from the ruling coalition more than a decade ago.

As deputy premier in the 1990s, Anwar was groomed by strongman prime minister Mahathir Mohamad to take power one day until a bitter row between them saw Anwar ousted in 1998, beaten, and ultimately jailed on sodomy and graft charges.

Thousands took to the streets in huge demonstrations calling for 'reformasi' (reform) and denouncing Anwar's ouster, which was widely viewed as politically motivated.

Anwar re-emerged years later at the helm of the opposition, inspiring an unlikely alliance of disparate parties to unprecedented parliamentary gains in 2008 general elections that shook the ruling establishment.

The new sodomy charge emerged shortly afterward. However, Anwar echoed many political observers in saying a guilty verdict would boost the opposition in the long run.

"I think they have made a big blunder (in bringing the charges)," he told AFP. He said the case also had shown that a recent promise by Najib to grant more civil liberties was merely an election ploy by an ultimately "authoritarian" regime.

But Anwar, looking tired, lamented the toll that his years of legal trouble have taken on his family, including his wife Wan Azizah Wan Ismail, who emerged as an opposition symbol during her husband's earlier political exile.

"I can see the anguish and sadness in their faces. But we have to endure," he said. Political law experts say Anwar has the right to stand in any upcoming elections until the appeals process is exhausted.