The long-running, politically charged trial of Malaysian opposition leader Anwar Ibrahim closed on Thursday with a judge setting January 9 for a verdict with potentially major implications.

Defence lawyers were allowed a final rebuttal on Thursday of the prosecution's charge that Malaysia's former deputy prime minister and one-time leader-in-waiting sodomised a 27-year-old male aide in June 2008.

Sodomy is illegal in Muslim-majority Malaysia and Anwar, 64, faces up to 20 years in jail if convicted.

Legal experts say he would also be barred from contesting polls expected to be called by Prime Minister Najib Razak within months, although others say he may be able to run if an appeal is pending.

"I will deliver my decision on January 9," judge Mohamad Zabidin Diah told a packed courtroom in the capital Kuala Lumpur, shortly after the defence rested in the trial which opened in February 2010.

Anwar, who was jailed a decade ago on a separate sodomy conviction that was later overturned, says the case was cooked up by Najib and is part of a pattern of legal harassment by the long-ruling coalition to ruin him politically.

"The process has not been fair. This is not a fair trial and we have adduced enough cogent, compelling, incontrovertible evidence to support that," Anwar told reporters after the trial ended.

"Having said that, we are still hopeful that sanity will prevail and the judge will decide based on the facts and the law."

Anwar alleges the case is a bid by Najib to decapitate an opposition alliance of ethnic Malay, Chinese and Muslim parties that found new strength rallying around the charismatic Anwar.

The sodomy allegation emerged shortly after the Anwar-led opposition secured historic gains in March 2008 parliamentary elections. "It doesn't make a difference -- in jail or outside, I will fight for justice," Anwar said.

Najib, who denies involvement in the case, must call elections by 2013, but speculation of early polls has mounted after he told his ruling United Malays National Organisation's (UMNO) congress last month that 'the time is near'.

Anwar's legal battles have cast a shadow over Malaysian politics for years. He had been groomed to take the helm of the multi-cultural nation but a bitter split with his boss, former Prime Minister Mahathir Mohamad, in 1997 led to Anwar's arrest the following year.

He was later convicted on sodomy and corruption charges widely seen as politically motivated, but was freed in 2004 after the sodomy conviction was overturned.

Whether or not Anwar can run in the coming polls, political observers say the ruling Barisan Nasional (BN) coalition apparently hopes his image -- and the opposition's -- will be fatally tarnished by a guilty ruling, especially among conservative majority Malay voters.

However, analysts say widespread perceptions among Malays -- who make up about 60 per cent of the country's 28 million people -- that Anwar is being persecuted have caused many to desert UMNO in favour of the opposition.

A guilty verdict could backfire on Najib, said James Chin, a political science professor with Monash University in Kuala Lumpur.

"Most people expect Anwar to be found guilty so the key will be in the sentence. If Anwar gets a harsh sentence, it will lead to strong anti-BN sentiments," Chin said.