LANSING (AP) — Michigan Gov. Gretchen Whitmer on Thursday threatened to veto legislation that would cut what are the country’s highest average auto insurance premiums, saying it falls short and urging the Republican-led Legislature not to send it to her desk without negotiated changes.

The Democratic governor said a state House-passed plan would not guarantee savings for motorists or go far enough in ending the use of non-driving factors to set rates. The GOP-controlled state Senate also approved a bill this week following years of legislative stalemates over the issue.

“They can either negotiate in good faith and send me a good bill that actually protects consumers while we also continue to negotiate the budget that fixes the damn roads, or they can send one of the current bills that fails to protect Michigan drivers and we can start all over again,” said Whitmer, who has proposed an unpopular 45-cents-a-gallon fuel tax increase to boost funding for deteriorating roads.

The House legislation — approved at around 2 a.m. Thursday during a marathon session — would allow motorists with health insurance to forego mandatory unlimited personal injury protection, or PIP, which only Michigan currently requires. Insurers would have to cut PIP rates, which can make up about half of a customer’s bill, by between 10% and 100% for five years, depending on the coverage chosen between $0 and $500,000. That could amount to an estimated $120 and $1,200 in savings for someone paying $2,400 annually per car, assuming the PIP fee accounts for half their bill, according to Republican projections.

Whitmer, who spoke with reporters after signing a bipartisan criminal justice measure into law, did not specify why she thinks the PIP reductions would not assure savings. But Democratic lawmakers said rates could go up after five years or insurers might just raise other portions of premiums in the meantime.

House Speaker Lee Chatfield, a Levering Republican, said his chamber delivered “real reform” with “hallmark” provisions that Democrats have long wanted, such as empowering state regulators to prohibit the inclusion of non-driving factors in rates.

Though GOP leaders and Whitmer indicated a willingness to talk, the situation remained in flux. Republicans oppose linking an auto insurance overhaul with Whitmer’s call for a major boost in transportation spending as part of her budget proposal.

Senate Majority Leader Mike Shirkey, a Clarklake Republican, said he would assess differences between the House and Senate plans over the weekend and make some decisions early next week.

“This doesn’t save minimal money. It gives people so many choices they can save lots of money,” he said.

Shirkey and the insurance industry oppose mandated rate rollbacks like those included in the House plan, but he said insurers may have some latitude and that “there is a landing spot for something.”

Senate Minority Leader Jim Ananich, a Flint Democrat, said Republicans did “walk our way” on some issues in the long-running debate over the no-fault insurance law, but divided government following years of GOP control means Democrats must “be a part of making this bill better.”

Under the House measure, people opting out of unlimited medical coverage would not have to pay much of what will soon be a $220 annual per-vehicle fee that reimburses auto insurers for expenses surpassing $580,000 for the severely injured.