The top attorneys in 15 states are considering going to court to challenge a Trump administration move to expand overtime pay requirements that they say doesn’t go far enough.

Democratic attorneys general in New York, Pennsylvania, California, and other states May 21 urged the Labor Department to rethink a proposal expected to make 1 million workers newly eligible for overtime pay. They want the DOL to instead fight to save an Obama-era regulation that was blocked in court by a separate group of states. The Obama rule would have made 4 million workers newly eligible for time-and-a-half overtime wages.

“It is absolutely on the table,” Minnesota Attorney General Keith Ellison told Bloomberg Law of a possible lawsuit to challenge the rule. “The Department of Labor is no friend of labor, and therefore, the attorneys general are going to have to be.”

The elected legal officials, in response to the department’s request for public comments on the proposal, argue in the letter that the department hasn’t done enough under the Administrative Procedure Act to justify abandoning the Obama rule. A court battle could stall the administration’s plan to have the rule in place before the end of President Donald Trump’s first term in office.

“The reason you put that APA stuff in the comment letter is to tee up a potential legal challenge down the road,” a lawyer inside one attorney general’s office told Bloomberg Law. The lawyer spoke on condition of anonymity to discuss plans that haven’t been finalized.

A group of 21 states, led by Nevada and Texas, convinced a federal judge in 2017 to block the Obama overtime rule. They argued that the proposal—which would have raised the salary threshold under which workers are automatically eligible for overtime pay to $48,000 from $23,500—would have forced states to cut government jobs to afford new overtime costs for public workers. The lawsuit was eventually combined with a similar complaint by the U.S. Chamber of Commerce and trade groups, which said the rule would cause private payrolls to skyrocket.

The DOL in May unveiled a new rule that would increase the overtime salary threshold to about $35,000 per year. Labor Secretary Alexander Acosta and other officials have said the threshold should be updated for inflation but that the court ruling forced them to seek a more moderate change.

The new proposal “would bring common sense, consistency, and higher wages to working Americans,” Acosta said in a statement announcing the proposed regulations.

New York Attorney General Letitia James and Pennsylvania Attorney General Josh Shapiro are leading the effort to oppose the new rule.