CHICAGO — A man who says J. Dennis Hastert, the former speaker of the House, molested him decades ago when the man was 14 filed a lawsuit against Mr. Hastert on Monday, saying he was owed $1.8 million of the money he had been promised as compensation for the abuse.

The suit, for breach of contract, says that Mr. Hastert promised to pay him $3.5 million for the pain and suffering that the abuse had caused, but failed to pay the full amount after being charged last year with federal crimes.

The name of the man was not made public in the lawsuit.

The suit was filed in Kendall County, Ill., on the edge of Chicago’s suburbs, where Mr. Hastert worked as a high school wrestling coach in the 1960s, 1970s and early 1980s, and where at least four members of the wrestling team have said he sexually abused them.

The suit adds to a mounting set of legal problems for Mr. Hastert, 74, who is expected to be sentenced on Wednesday in federal court here after pleading guilty to a banking violation tied to the abuse.