Ivan Basso has quit the Discovery Channel team following the reopening of an investigation into his role in a Spanish doping scandal.
Basso only joined Discovery Channel in November
The Giro d'Italia champion asked to be released immediately from his contract, citing personal reasons.
He faces an Italian Olympic Committee hearing on Wednesday on charges of having used or attempted to use a banned substance or method.
Basso, who has always denied doping, was suspended by his team last week.
He said: "It is important that everyone knows this was 100% my decision. Nobody asked me to leave.
"The team is trying to find a new sponsor and win bike races, and my situation is a distraction to both of those goals."
This was a very difficult decision, for me and my family,
but I think it is the right thing to do
The 29-year-old signed a two-year contract in November to ride for the US outfit.
Basso was one of 50 riders implicated in last year's Operation Puerto, which led to his exclusion from the Tour de France.
His name turned up on a list of cyclists who allegedly had contact with a Spanish doctor accused of running a blood doping clinic in Madrid.
Basso was cleared of involvement by the Italian Olympic Committee and the Italian cycling federation in October.
However, Italian doping investigators have reportedly obtained bags suspected to contain Basso's blood from Spain and want to compare them with his DNA.
This month, a DNA sample of 1997 Tour de France champion Jan Ullrich was matched to blood bags seized in the scandal.
The now-retired German has denied using any banned substances.
Cycling's governing body the UCI has refused to comment on reports that fresh evidence in the Operation Puerto case implicates dozens more cyclists.