KUALA LUMPUR, April 21 (AFP) - Former Malaysian deputy premier Anwar Ibrahim threatened Friday to abandon his sex trial after the judge ruled out an appearance by Prime Minister Mahathir Mohamad as a witness.

"There is not an iota of evidence by any witnesses so far to show that Dr. Mahathir is involved in a political conspiracy to topple (Anwar)," said high court Justice Arifin Jaka.

"Under these circumstances, it is futile to call Dr. Mahathir to give evidence in this trial."

Defence lawyer Christopher Fernando later told Arifin that Anwar's "confidence in the administration of justice is completely eroded" by the ruling.

"His immediate reaction now is to abandon this trial as he sees his chances of succeeding in this trial are next to zero," Fernando said. He sought an adjournment to allow Anwar time to consider the matter.

Arifin ruled that the hearing should resume on Wednesday.

Had Mahathir been forced to appear in court, it would have been the first face-to-face encounter between the two politicians since Anwar was sacked by the premier in September 1998.

Anwar, jailed six years' last April for abusing his powers, says he is the victim of a high-level conspiracy because he intended to expose corruption and was seen as a political threat to the premier.

He is now on trial for sodomy, punishable by up to 20 years in jail.Earlier, Arifin said he treated Mahathir "just like any other citizen without any privilege" in making his decision but added that the defence had failed to satisfy him on the relevancy of the premier's testimony.

He ordered a subpoena for Mahathir to appear as a witness be set aside.As the judge was reading his decision, Anwar was heard to exclaim: "My God!"

He jumped up from his seat immediately after Arifin delivered his ruling and said angrily: "Dr. Mahathir should have the moral courage to come."Where is the justice in this court? You did not consider at all my views.

We have a judgement that takes Dr. Mahathir's views as the gospel truth," he said.

"He has been roaring like a lion to the whole world and now, he is like a mouse."

Fernando told reporters that the defence team was "quite shocked" by the ruling which would set back Anwar's case as the premier's evidence could have "thrown light on the grey areas."

He said Anwar was considering abandoning the trial and halting defence submissions but added that counsels felt he should go on with it.

"I don't think a conviction can be sustained on the evidence that has been adduced," Fernando said, adding that he would secure final instructions from Anwar next week.

In a separate handwritten note given to reporters by family members, Anwar condemned the premier for not having the courage to "come clean and defend the scandalous and defamatory remarks" he had made.

"There is no rational decision for his adamant refusal to testify in court other than his fear that his evil machinations, the political conspiracy of using the instruments of goverment including to fabricate evidence would be further exposed," Anwar said.

"Even more insidous is that this decision shows that Dr. Mahathir can freely act with complete impunity vis-a-vis the judiciary."

Anwar said the premier was now the "sole Malaysian immune from legal process."

"Dr Mahathir's failure to appear in court would deprive me of the right to adduce evidence and the opportunity of rebuttal. He is privy to the facts and events behind this web of intrigue and the entire sickening charade," he said.

Anwar said the court's decision had compromised the principle of justice and flawed the legal process.

"It underscores the conditions that Malaysians are living in despite the democratic facade and paraphernalia of a system of justice," he added.