All but one of the colleagues asked to speak in defence of the NatWest Three fraud suspects have refused to meet the accused's lawyers, it has emerged.
Gary Mulgrew, from Brighton, and former colleagues David Bermingham and Giles Darby were extradited to Texas, USA, in July last year on fraud charges relating to the collapse of US energy giant Enron.
The trio deny stealing $7.3 million from their former employees Greenwich Natwest, a division of Natwest, with the help of former Enron employees.
Lawyers for the three wrote to 36 current and former employees of the Royal Bank of Scotland, which now owns NatWest, according to the Times newspaper.
Just one potential witness - whose identity has not been revealed - was willing to be contacted about giving evidence at the trial.
A spokesperson for the NatWest Three said: "They are particularly angry about having to face trial in the US rather than in the UK, and since much of what they argued in court in the UK about how their ability to defence would be compromised in Texas has proven to be true."
The 36 bankers are being advised by RBS lawyers Travers Smith in London.
An RBS spokesman said: "In a case such as this, it is a matter for any individual whether they wish to accept such a request, and in view of the ongoing proceedings, it would be inappropriate to comment further."
Neil Coulbeck, another former colleague of the NatWest Three, killed himself over fears of being extradited to the US to face trial, also over the Enron scandal.
The Nat West Three, who are under house arrest in Houston, are each charged with seven counts of fraud.
They are alleged to have conspired with Andrew Fastow, Enron's former finance director, to execute a complex financial scam that cheated NatWest out of several million dollars.
Mr Fastow, jailed for six years for his role in the collapse of Enron, has agreed to testify against the three men in return for a lighter sentence.
The trial is scheduled to begin in October and could end with each of the NatWest Three serving 35 years in jail.
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