A New Mexico entrepreneur says he is sponsoring a $2.5 million-purse endurance horse race from St. Joseph, Mo., to Sacramento, but critics are fiercely attacking the proposed event.

Barry Ward, who runs Vision Sports Inc. of Albuquerque, N.M., says 408 entrants have signed up so far to pay $5,000 each to compete in an equine "spectacle" very loosely patterned after the legendary Pony Express. Ward said it would start Sept. 5 and arrive in Old Sacramento Sept. 27.

However, Ward's plans for "Bonanza '88" are encountering problems. For instance, the California Highway Patrol has answered Ward's intentions to run the finale down U.S. Highway 50 with a curt "no way."

Veterinarians have lambasted Ward for planning to conduct incomplete medical examinations, horse lovers have accused him of promoting animal cruelty and Sacramento officials whom Ward claims to have contacted say they have never heard of him.

In addition, nationally distributed endurance organizations have taken Ward to task for offering a number of cash purses, including $300,000 to the winner and $20,000 to the 25th-place team.

But Ward, 64, remains undeterred.

In fact, he has distributed a report proclaiming that a "pre-race meeting" for contestants will be held in Sacramento, April 30-May 1.