The union expressed concern in May about the lack of offers to the home run king. Filing a grievance would trigger proceedings before arbitrator Shyam Das.
Union general counsel Michael Weiner confirmed the deal with Major League Baseball, which was first reported by murraychass.com.
"There were numerous things that occurred that made me believe that the clubs were acting in concert," Bonds' agent, Jeff Borris, said Thursday. "When I testify as a witness in the case, I will delineate each and every one of them."
Bonds was indicted last Nov. 15 on charges related to 2003 grand jury testimony during which he denied knowingly using performance-enhancing drugs. No team signed Bonds when he became a free agent after the 2007 season.
"We have the agreement about the timing of a potential grievance," Weiner said. "Our investigation revealed a violation of the Basic Agreement. It's a violation of the Basic Agreement related to Barry Bonds and free agency."
Weiner said the section that had been violated was Article XX (e) of the collective bargaining agreement, which states, in part: "Players shall not act in concert with other players and clubs shall not act in concert with other clubs." Weiner would not say how long the agreement runs to allow the union to file a grievance.
Baseball attorneys repeatedly have denied that teams acted in concert against Bonds. Management lawyer Dan Halem said Thursday that MLB would have no additional comment.
Bonds pleaded not guilty to 14 counts of making false declarations to a federal grand jury and one count of obstruction of justice, and his trial is scheduled to start March 2. Any grievance is likely to follow the trial.
"The timing of the filing of the case is between the players' union and the commissioner's office," Borris said.
After spending a lot of time during the first half of 2008 trying to get Bonds signed, Borris has stopped his efforts.
"I am convinced based on MLB's actions in 2008 that they will never let him wear a major league uniform ever again," he said.
The players' association won three collusion grievances in which owners were found to have conspired against free agents following the 1985, 1986 and 1987 seasons. Management agreed in 1990 to settle those cases for $280 million and also agreed to a provision that future collusion would be subject to triple damages.