WASHINGTON — U.S. Sen. Bill Cassidy found bipartisan agreement on offering working Americans paid family leave at a Wednesday subcommittee hearing he chaired, with conservatives and liberals chiming in favor of doing something.

The latest push to expand paid maternity and family leave comes after months of lobbying by Ivanka Trump, President Trump's oldest daughter and a special White House adviser who's tried to make the policy one of her signature issues.

The devil, though, is in the details. Democrats and Republicans broke over how to pay for the time off.

Sens. Joni Ernst, R-Iowa, and Marco Rubio, R-Florida, have proposed using Social Security money to cover the cost of maternity leave, with any time off docked from future Social Security retirement benefits.

A number of Democrats, meanwhile, have signed onto a proposal that would levy a payroll tax to cover paid time off for new parents and those caring for ailing family members.

Details of both proposals are still being hammered out. But Democrats said Wednesday their plan would offer wider coverage to workers — covering illness and time off to care for aging parents — while the Ernst-Rubio proposal has so far focused on parental leave.

Cassidy, who's met with Ms. Trump on the issue, expressed reservations any new payroll taxes — arguing looming shortfalls in the Social Security retirement program might also require payroll tax hikes — and worried that generous benefits would put small businesses in a bind if too many workers took time off.

"It’s false compassion to put forward a program that can’t be sustained," Cassidy said.

But Cassidy said he's still looking into Ernst and Rubio's idea to dock future Social Security retirement benefits to cover time off and hasn't yet signed on to that proposal, either.

Cutting into a worker's future Social Security benefits appeared to be a non-starter for some Democrats, who called that a first step toward gutting or privatizing the social insurance and retirement program.

"Using your retirement security to fund paid time off from work when you have a child is not paid family leave at all," said Sen. Sherrod Brown, D-Ohio. "It's robbing from your retirement to be able to care for loved ones now."

Any legislation would need the support of at least 60 senators to make it into law, meaning Republicans will need sizable Democratic support.

Lawmakers nonetheless expressed optimism – if muted — about the growing bipartisan agreement on offering some sort of paid family leave, despite the sizable policy differences.

Brown called the hearing "baby steps" toward an eventual nationwide scheme. Cassidy, meanwhile, said Ms. Trump's support on the issue had built political interest in legislation.

Follow Bryn Stole on Twitter, @BrynStole.