Lance Armstrong is set to be stripped of his seven Tour de France titles and banned from sport for life after deciding to not to opt for arbitration to fight the charges brought against him by the United States Anti-Doping Agency (USADA).

In a statement published on his website in which he continued to protest his innocence, the 40-year-old said: “There comes a point in every man's life when he has to say, ‘Enough is enough.’ For me, that time is now,” describing USADA’s pursuit of him as an “unconstitutional witch hunt.”

USADA, which will issue a full statement today, has already confirmed that it intends to ban Armstrong for life and to take away the record seven Tour de France titles he won between 1999 and 2005.

USADA CEO Travis Tygart said: "It is a sad day for all of us who love sport and our athletic heroes. This is a heartbreaking example of how the win-at-all-costs culture of sport, if left unchecked, will overtake fair, safe and honest competition."

Earlier this week, US district judge Sam Sparks, sitting in Armstrong’s home town of Austin, Texas, rejected a lawsuit brought by him and confirmed that USADA had jurisdiction over the case, rather than the UCI or USA Cycling.

The World Anti-Doping Agency (WADA) had backed USADA's stance. Both the UCI and USA Cycling are signatories to the World Anti-Doping Code (WADC), which provides that the national anti doping agency is the competent body in a case such as this.

As a result, Armstrong had to choose by midnight Colorado time (where USADA is based) yesterday whether to contest the charges through arbitration or accept USADA’s sanctions.

Despite that decision, in which Judge Sparks did express reservations about USADA’s motives, Armstrong’s legal team continued to insist yesterday that USADA lacked jurisdiction in the case.

His attorney Tim Herman writing a strongly worded letter to the agency saying that its case against him should be submitted to the UCI or the Court of Arbitration for Sport (CAS) to deal with.

Armstrong’s own statement suggests, however, that certainly as far as any proceeedings from USADA are concerned, the battle is over.

At the end, he said: “Going forward, I am going to devote myself to raising my five beautiful (and energetic) kids, fighting cancer, and attempting to be the fittest 40-year old on the planet.”

There does remain the possibility, however, that the UCI, which had contested USADA's jurisdiction, might decide to challenge any formal decision from it at the Court of Arbitration for Sport.

In a statement, the governing body said: "The UCI notes Lance Armstrong’s decision not to proceed to arbitration in the case that USADA has brought against him.

"The UCI recognises that USADA is reported as saying that it will strip Mr. Armstrong of all results from 1998 onwards in addition to imposing a lifetime ban from participating in any sport which recognises the World Anti-Doping Code.

"Article 8.3 of the  WADC states that where no hearing occurs the Anti-Doping Organisation with results management responsibility shall submit to the parties concerned (Mr Armstrong, WADA and UCI) a reasoned decision explaining the action taken.

"As USADA has claimed jurisdiction in the case the UCI expects that it will issue a reasoned decision in accordance with Article 8.3 of the Code.

"Until such time as USADA delivers this decision the UCI has no further comment to make."

The specific allegations against Armstrong himself, including the testimony of former team mates who have never been formally identified by USADA although their names have been the subject of press speculation, will not now be presented in an arbitration hearing.

However, it is likely that much of that evidence will be heard at other hearings including that relating to Armstrong's manager at US Postal and elsewhere during the period concerned, Johan Bruyneel, who himself has been charged by USADA but who chose the arbitration route.

Reacting to the news of Armstrong's decision on his personal website, Bruyneel, now manager of RadioShack-Nissan, wrote: "Today, I’m disappointed for Lance and for cycling in general that things have reached a stage where Lance feels that he has had enough and is no longer willing to participate in USADA’s campaign against him. Lance has never withdrawn from a fair fight in his life so his decision today underlines what an unjust process this has been.

"I hope that it will soon be determined that the case that USADA initiated against me should never have gotten as far as it has. Due to the sensitive nature of legal proceedings, I have been advised that it would be inappropriate for me to comment further at this stage."

John Fahey, President of WADA, reacted to the news by saying that he believed Armstrong's actions proved there was "substance" to USADA's allegations.

"He [Armstrong] had the right to rip up those charges but he elected not to, therefore the only interpretation in these circumstances is that there was substance in those charges," Fahey, quoted on Eurosport, told Reuters.

"My understanding is that when the evidence is based upon a career that included seven Tour de France wins then all of that becomes obliterated."