Donaghy was to surrender at Brooklyn federal court, the person said on condition of anonymity because charges had not been made public yet.

NBA spokesman Tim Frank told the AP the league was informed today that Donaghy would plead tomorrow but was given no further information.

Donaghy's attorney, John Lauro, and federal prosecutors declined to comment. NBA commissioner David Stern said last month the referee's lawyer told the league his client was contemplating a plea.

Besides allegedly placing his own wagers, investigators also examined whether Donaghy provided inside information to others, including referees' schedules. The referee had a gambling problem and was approached by low-level mob associates through an acquaintance, a law enforcement official said.

The FBI first contacted the NBA on June 20 to talk about a referee alleged to be gambling on games, and the two sides met on June 21, Stern said last month. Donaghy resigned July 9 after 13 years as a referee, though Stern said he would have fired him sooner but was told it might affect the investigation.

Stern blamed a "rogue, isolated criminal" for the betting scandal that has devastated the league and threatened the credibility of every referee.

Donaghy was rated in the top tier of officials, Stern said, and there was nothing suspicious about the frequency of his foul calls. He was assigned to work in the second round of the playoffs, with his last NBA game coming during the Phoenix-San Antonio Western Conference semifinal.

No other NBA officials or players were expected to be involved in the scandal, which Stern called the "most serious situation and worst situation that I have ever experienced either as a fan of the NBA, a lawyer for the NBA or a commissioner of the NBA."