The National Highway Traffic Safety Administration seems to be working against itself in California.

The state's General Assembly and Senate have approved similar bills that require the use of seat belts in passenger cars -- legislation that could help NHTSA's drive to encourage more Americans to buckle up.

California legislators are certain that the minor differences between the two versions of the bills can be easily reconciled in conference committee. But the legislators say that the bills are trapped and in jeopardy because Transportation Secretary Elizabeth Hanford Dole refuses to rule on their validity.

At issue is a quirk in a July 1984 DOT regulation that could force state legislatures to choose between passing mandatory seat belt laws or mandatory automatic crash protection laws to protect their residents.

The regulation says that automatic crash protection devices, such as airbags, must be available in cars sold in the United States beginning Sept. 1, 1986. By the 1990-model year, the automatic systems must be available in all cars sold in this country.

But the rule has a big escape hatch. It says that the provision would be rescinded if states with two-thirds of the nation's population pass laws by April 1, 1989 that require their residents to use seat belts when they drive.

The problem is that many state lawmakers, including many in California, want both mandatory-use laws and automatic crash protection. The regulation, they say, forces them to make an unwelcome choice. As a result, some legislatures have resorted to approving mandatory-use laws that would encourage drivers and passengers to use seat belts, but that are too weak by DOT standards to offset the federal rule requiring automatic crash protection.

The California bills are designed to do just that. But California Assembly Speaker Willie Lewis Brown Jr. says he believes that DOT intends to include the weak seat belt laws when it determines whether enough states have passed laws to offset the automatic device provision. If so, Brown said, passage of such a law in California, with about 10 percent of the nation's population, would give a big boost to those forces -- auto makers chief among them -- seeking to use seat belt laws to do away with automatic crash protection requirements.

As a result, Brown is keeping the two bills locked up in conference committee until Dole assures him that they are too weak to block the automatic crash protection rule. In a June 25 letter, Brown demanded a clarification from Dole.

"Because certain statements of the department's employes and correspondence to members of Congress seem to indicate that your minimum criteria are neither clear in their application nor immutable, I must obtain an unequivocal answer to you on two distinct questions," Brown wrote.

"First, does my legislation . . . meet your minimum criteria which would allow this California legislation to be counted in repealing the federal passive restraint standard? Second, will you reject attempts to amend or eliminate your minimum criteria . . . . ?"

A DOT spokesman said yesterday that Dole responded, but that the response was unsatisfactory to Brown.

Dole said she could not rule on certification of state seat belt laws until after the U.S. Court of Appeals for the District of Columbia decides a case challenging the regulation.

"The response that he received from Mrs. Dole was so murky, he just sent the whole thing back to committee," a spokesman for Brown said yesterday.

Dole, who was returning from a trip to Japan, was unavailable for comment.

So far, 15 states, with 42 percent of the nation's population, have passed laws requiring motorists to use seat belts.