New Jersey's Senate president is accusing the state's largest teacher's union of threatening to withhold political contributions in exchange for a vote on requiring quarterly pension payments.

Democrat Steve Sweeney on Wednesday said that leaders of the New Jersey Education Association called Democratic county chairmen and threatened to withhold political contributions unless the Senate passes a proposed amendment ramping up pension payments by the state.

Sweeney also called on the U.S. attorney and New Jersey attorney general to investigate the union's action as criminal.

The NJEA said in a statement it did nothing illegal and Sweeney broke a promise to pass the amendment.

Sweeney, an executive with the ironworkers union and possible gubernatorial candidate, called the action "intolerable."

The proposal must be passed this week to get on the ballot.