Former top New Zealand cyclist Stephen Swart has given evidence in a case brought by Tour de France star Lance Armstrong in the United States and is to testify in a defamation case in London.

Swart, who was a Motorola teammate of Armstrong's, alleges that in 1995 he and the seven-time tour winner took erythropoetin (EPO), a banned red-cell-booster which improves endurance.

Swart, who has lived in Auckland since retiring from professional cycling at the end of 1995, told the Weekend Herald he had appeared at a closed arbitration hearing in Dallas earlier this month at the request of SCA Promotions, a company which provides risk cover for promotional contests.

His evidence, before a panel of three lawyers selected by Armstrong and SCA, was videotaped. Swart is self employed and works in the construction industry.

Armstrong, ranked the world's third most powerful sportsman in 2005 by Forbes magazine, went to court to force the arbitration after SCA failed to pay the cyclist a US$5 million ($7.3 million) bonus for winning a record sixth Tour de France in 2004. It had paid US$4.5 million for Armstrong's previous tour wins.

SCA withheld payment because it wanted to investigate doping claims in a book, L. A. Confidentiel: Les secrets de Lance Armstrong, co authored by Sunday Times chief sports writer David Walsh.

The book makes a circumstantial case that Armstrong had taken performance-enhancing drugs, including EPO, human growth hormone and steroids, and covered it up.

In the book, Swart says the decision to take EPO was made during the early part of 1995 by some senior team riders including himself and Armstrong.

The book is at the centre of three cases brought by Armstrong.

In June 2004, the cyclist brought a defamation suit in London against the Sunday Times for an article it printed about the book.

In September 2004, he filed a defamation suit in France against the book's publisher and authors, and a magazine that printed an excerpt, and in the same month, he went to court in the United States to force SCA into arbitration. Armstrong's lawyers say his record of negative drug tests during the 2004 tour was all the verification SCA required.

The Sunday Times defamation case, originally scheduled for last November, has been delayed by pre-trial manoeuvring. Swart confirmed he has agreed to a request by the newspaper to testify.

The newspaper won an appeal to restore the use of "qualified privilege" which means it will argue it acted responsibly, that its story raised reasonable questions that were in the public interest.

The stakes are high for both the Texan who survived cancer to win the Tour de France seven times, and for Walsh, winner of three British Press Awards for Sports Writer of the Year.

There is the prospect new evidence may emerge during the hearings.

In the book, Walsh and co-author Pierre Ballester, provided no source for the charge that Armstrong admitted to his cancer doctors in 1996 that he had used EPO and human growth hormone.

Two of those whom the authors said were present during the alleged hospital conversation - Swart and Armstrong's former teammate Frankie Andreu and his wife, Betsy - have confirmed they have been subpoenaed by SCA and asked to testify in the Sunday Times case.