Former top Fifa official Chuck Blazer has admitted that he and others on the executive committee agreed to accept bribes in connection with the choice of South Africa as 2010 World Cup hosts.
The American said he also facilitated bribes over the 1998 event.
The admissions come in a newly released transcript from a 2013 US hearing in which he pleads guilty to 10 charges.
The US has launched a wide-ranging criminal case that engulfed Fifa and led President Sepp Blatter to resign.
Last week US prosecutors indicted 14 people on charges of bribery, racketeering and money laundering. Four others had already been charged, including Mr Blazer.
The US justice department alleges they accepted bribes and kickbacks estimated at more than $150m (£97m) over a 24-year period.
Seven of the 14 were top Fifa officials who were arrested in Zurich, Switzerland, as they awaited the Fifa congress. Two were vice-presidents.
In another development, former Fifa Vice-President Jack Warner, who is among those charged, said on Wednesday he had documents linking Fifa officials to the 2010 election in Trinidad and Tobago.
"I will no longer keep secrets for them who actively seek to destroy the country," he said in a paid political broadcast on Wednesday evening.
Mr Warner, who denies charges against him, said he feared for his life, but would reveal everything he knows about the alleged corruption.
'Kickbacks'
The details of Mr Blazer's guilty pleas came as prosecutors unsealed the transcript of the 2013 hearing in the Eastern New York District Court. The admissions are part of a sentencing deal with prosecutors.
Mr Blazer was the second highest official in Fifa's North and Central American and Caribbean region (Concacaf) from 1990 to 2011 and also served on Fifa's executive committee between 1997 and 2013.
