Florida Sen. Marco Rubio on Friday afternoon called an offer by Republican leaders to increase the refundable portion of the child tax credit in their tax legislation a "solid step" but did not commit to voting for the bill.

The refundable part of the credit would increase from $1,100 to $1,400, a Republican lawmaker told the Washington Examiner. That change would extend more tax benefits to families with modest incomes.

Friday afternoon, Rubio called the compromise "a solid step toward broader reforms." He stopped short of saying outright that he would vote "yes" on the underlying tax bill.

But there is still much more to do in the months and years to come. The progress made on the Child Tax Credit would not have been possible without the support of @SenMikeLee, @SenatorTimScott, and @IvankaTrump. — Marco Rubio (@marcorubio) December 15, 2017



Other GOP senators sounded confident Rubio would vote for the bill next eek.

There are changes in this bill that I think conform to some of the things he asked for," said Sen. Mike Enzi, R-Wyo.

"I'm confident we're going to have the votes to pass it next week," said Sen. Pat Toomey of Pennsylvania, another conferee, when asked if the change would secure Rubio's vote.

The Senate-passed version of the bill included a doubling of the child tax credit, to $2,000 per child, a provision supported by Rubio. But only $1,100 of that would be paid out to families with no income tax liability, and Rubio was looking to increase that amount.

Rubio had sought to increase that amount, saying that he would be willing to compromise short of the full $2,000. He also aimed to make the credit applicable to the first dollar of income earned by the taxpayer, instead of current language that would only apply after the first $2,500 earned.

Rubio also wanted the credit to apply to payroll tax liability in the case the taxpayer had no income tax liability.

The exact terms of the expanded credit were not clear as of Friday afternoon, nor were the changes made elsewhere in the bill to pay for it.

With Utah’s Mike Lee, Rubio offered an amendment during Senate passage that would have made the credit fully refundable against payroll taxes, paid for by setting the corporate tax rate at 20.94 percent, rather than 20 percent.

That amendment was rebuffed, but Rubio and Lee voted “yes” on the bill.

When Senate-House negotiators then raised the corporate income tax by one percentage point to lower the top income tax rate, however, Rubio objected.

At least one Republican raised an objection to the changes made to accommodate Rubio: Sen. Lindsey Graham of South Carolina.

Social Security has never been a welfare program and I don’t want it to become one.



Using general revenue dollars to pay someone’s Social Security contribution is bad policy. — Lindsey Graham (@LindseyGrahamSC) December 15, 2017



Graham said on Twitter that it was "bad policy" to use general tax revenue to pay for individuals' Social Security contributions, which would be necessary to offset the payroll tax reductions from the refundable credits.

A spokesman for his office, however, said that Graham's tweets shouldn't be interpreted as a sign that he will vote against the tax bill.