US prosecutors have made public their 2013 plea agreement with Chuck Blazer, revealing that the former FIFA executive committee member had been secretly providing authorities information for nearly two years before he admitted guilt.

Blazer, who had been a FIFA executive committee member from 1997 to 2013, secretly pleaded guilty in November 2013 to 10 counts including conspiracies to commit racketeering, wire fraud and money laundering.

According to a redacted transcript of his plea hearing, Blazer admitted that he and other officials took bribes in connection with the 1998 and 2010 World Cups.

Blazer also admitted to accepting bribes and kickbacks related to five different editions the Gold Cup between 1996 and 2003.

He also admitted to committing tax evasion and to working with others to transfer the money between accounts in an effort to conceal the kickback schemes.

Blazer, 70, is one of four individuals who had secretly pleaded guilty in the years before the case was announced on May 27.

He has become a key cooperating witness in the probe, which has engulfed FIFA and led the governing body's president Sepp Blatter to announce his resignation.

FIFA President Sepp Blatter has said he will resign and a new leader will be chosen this year [Getty Images]

This agreement with the key cooperating public witness was revealed by prosecutors after a federal judge in Brooklyn, New York, ordered it unsealed at the request of media outlets following the indictment of nine current and former FIFA officials and five corporate executives.

The document revealed that Blazer, the former general secretary of CONCACAF, football's governing body in North and Central America and the Caribbean, began providing prosecutors information as early as December 2011.

Under the agreement, Blazer agreed to provide prosecutors information, turn over any documents he possessed related to the probe, participate in undercover activities and testify at trial.

The Justice Department had initially opposed making the agreement public, arguing that confirming that Blazer was a cooperating witness would prejudice its investigation and jeopardise his safety.

But US District Judge Raymond Dearie rejected those arguments, saying prosecutors had failed to meet their "high burden" to establish the document should remain sealed.

Source: Al Jazeera and agencies