The American ambassador to Thailand warned that country's leader last year that associates of suspected Russian arms merchant Viktor Bout tried to prevent his extradition to the U.S. and were behind bribery schemes and a plot to arrest U.S. officials, according to a secret diplomatic memo released Wednesday by WikiLeaks.

In a February 2009 meeting with Thai Prime Minister Abhisit Vejjajiva, Ambassador Eric John told of "serious concerns that Bout's associates had been able to influence testimony" during the suspect's drawn-out hearings on extradition to the U.S.

"Russian supporters have been using money and influence in an attempt to block extradition," John told Abhisit, according to the cable.

Bout was jailed in Bangkok in March 2008 after he was arrested in a sting by U.S. narcotic agents on charges of conspiring to sell weapons to a terrorist group. He fought extradition for more than 2 1/2 years until Thai officials ordered him sent to the U.S. last month. Bout was flown to New York to face trial and is being held in a federal detention facility.

Bout, 43, gained notoriety as the alleged armorer for African dictators and the Taliban's mullahs. The United States, its allies and the U.N. tried in vain to scuttle his worldwide operation for more than a decade while Bout built a massive fleet of more than 60 cargo planes and amassed a fortune estimated by American investigators at more than $6 billion.

John told the Thai leader during their session that "bribery had infected the Bout proceedings" and warned that false testimony could lead the Thai court to "possibly deny extradition."

The ambassador told Abhisit that U.S. officials had learned of a scheme to "arrest and embarrass" two federal Drug Enforcement Administration agents who were assigned to the Bout investigation. According to John, unnamed plotters aimed to have the two agents arrested, apparently by Thai law enforcement, "on meritless charges participating in illegal recordings of Bout on the day of his arrest."

Much of the federal prosecution's case against Bout is expected to be based on extensive wiretaps of Bout's conversations in Bangkok and elsewhere around the world. The DEA also employed several undercover informants to lure him to Thailand. A former Bout associate who was arrested with him in a Bangkok luxury hotel is expected to testify against him.

John also detailed false testimony from several witnesses for Bout who had claimed he went to Bangkok "to conduct official business with the Thai government" in connection with a Russian submarine project.

The cable reported that Abhisit agreed to deal with the "irregularities" in the extradition proceedings through Thai channels and asked for the identities of the bribery plotters. U.S. officials provided the names, the cable reported.

Six months later, Bout was still fighting his extradition and U.S. officials were growing frustrated, according to a second cable released Wednesday. The Aug. 13, 2009, document, also marked "secret," describes an Aug. 11 Thai court decision against extradition as "disappointing" and based on "dubious legal reasoning."

John vented his disappointment with the Thai foreign minister, and other officials advised that President Barack Obama and other top administration officials needed to weigh in with the Thai government.

Discussion of a telephone call from Obama to Abhisit "has been under way for some time; they have not spoken in the seven months both have been in office," embassy officials noted in the cable. "We suggest that the call be accelerated and that it include a serious discussion of our concerns over the implications of the Bout verdict, as outlined above. We believe POTUS involvement on Bout would have significant effect here."

POTUS means president of the United States.

Secretary of State Hillary Rodham Clinton later brought up the Bout case with Thai leaders, but there has been no public indication that Obama also raised the case with Abhisit.