KUALA LUMPUR, Malaysia (CNN) -- The United States has added its voice to the mounting international condemnation over jailed Malaysian politician Anwar Ibrahim's sodomy conviction and subsequent nine-year prison sentence.
As international outrage mounted on Wednesday, Forum-Asia, the Bangkok-based human rights group, said the verdict announced on Tuesday by Malaysian High Court Judge Arifin Jaka showed a disregard for the rule of law.
Meanwhile, Aliran, a Malaysian group, called the sentence "an extreme form of punishment."
Arifin ended Anwar's nearly yearlong sodomy trial on Tuesday when he ruled the former Malaysian deputy prime minister and finance minister and his adopted brother, Sukma Darmawan, were guilty of sodomizing Anwar's former driver, Azizan Abu Bakar.
Arifin sentenced Anwar, 52, to nine years in prison, to be served consecutive to the six years he is serving for a corruption conviction. After serving the 15 years, Anwar will be disqualified from holding public office for five years.
Sukma, 39, was sentenced to six years in prison and four strokes of a cane. The cane is only applied to people under age 49. However, his sentence was suspended pending appeal. Anwar's lawyers also said they would appeal.
Anwar, sacked from government in September 1998 by Prime Minister Mahathir Mohamad, has denied any wrongdoing, and said the trials were part of a plot by Mahathir to remove him from politics.
The United States, Canada, the International Commission of Jurists, or ICJ, and World Bank President James Wolfensohn joined Malaysia's opposition, Australia and New Zealand in condemning Arifin's ruling.
U.S. State Department Spokesman Richard Boucher said the United States was "outraged" by Anwar's conviction, and that the cooperative relationship with Malaysia had been impeded by Malaysia's poor record on human rights.
"This verdict doesn't help matters," Boucher said on Tuesday.
"(Both convictions) cast serious doubt on the impartiality and independence of the Malaysian judiciary," Boucher said. He called Anwar a "victim of political conspiracy."
Earlier Tuesday, Marie-Christine Lilkoff, spokeswoman for Canada's Foreign Affairs office, said the convictions resulted from flawed trials. She said Canadian officials were concerned about Malaysia's judicial system.
"The erosion of confidence in the rule of law not only threatens the rule of democracy in Malaysia, but could also damage the nation's long-term economic prospects," she said.
Wolfensohn said he was "distressed" by the ruling.
"Anwar is not only a friend and valued colleague, he was a distinguished chairman of our Development Committee, and a man who believed in speaking his mind," Wolfensohn said.
The Geneva-based ICJ -- composed of 45 jurists who defend the rule of law internationally -- said the ruling was politically motivated.
"Anwar's mistreatment, including his beating during detention, was contrary to international human rights standards," the group said.
Shortly after the verdict was announced, Joe Saunders spokesman for U.S.-based Human Rights Watch said the ruling was a "blow to justice ... a real step backwards for Malaysia."
Meanwhile, Australian Foreign Minister Alexander Downer said he was saddened by the verdict, and New Zealand Foreign Minister Phil Goff said he had "deep concern" about the trial's fairness.
Undaunted by the ruling, Anwar's backers vowed during a birthday celebration on Wednesday for Anwar -- who turns 53 on Thursday -- to fight to remove Mahathir from office.
"We will once again rock this nation with our desire that Mahathir Mohamad resign as prime minister of Malaysia," Mohamed Ezam Mohamed Nor, youth leader in the National Justice Party, told a crowd of sympathizers.
"We want to tell Mahathir that we are not afraid. We will rise with a new spirit to ignite awareness in this whole country," said Mohamed Ezam as nearly 400 people thumped tables and shouted "Reformasi," the battle cry for reform.
CNN State Department Producer Elise Labott, CNN Correspondent Kasra Naji, CNN Correspondent Lisa Barron, The Associated Press and Reuters contributed to this report.