Ninety-four percent of union members voted to reject an offer made in late April. About 800 members of the union local went on strike May 1.
In the second six-year offer, pay and benefits were unchanged, The Wall Street Journal reported Wednesday.
Caterpillar is also seeking to adjust wages for those hired after May 2005 and to freeze wages for those hired before that date.
The latest contract offer, turned down Wednesday by members of the International Association of Machinists and Aerospace Workers, demanded a larger health insurance contribution from workers. It would also shift the workers' current pension plan to a standard 401k retirement savings plan, the Journal said.
Workers were offered $1,000 as a bonus for ratifying the contract and bonus pay of up to $2,100 if the factory hit various performance targets in the second quarter.
Union leaders advised members to turn down the contract, which they said offered too few changes from the first offer. They also said the goals set for the performance bonus were unrealistically high.
IAM official Steve Jones said Caterpillar has apparently decided to stop negotiations, at least temporarily.
After the vote, Jones said, union leaders told the company they were ready to continue talks, but the company said there was no point in doing so.