The White House on Thursday said it will work with Sen. Marco Rubio, R-Fla., to address his concerns about the current GOP tax bill "until we get the job done."

Rubio told congressional leaders earlier in the day he will vote against the $1.5 trillion tax plan negotiated by House and Senate Republicans unless the child tax credit is further expanded.

"We're really proud of the work that we've done already up until this point with Sen. Rubio, already doubling the child tax credit to $2,000," White House press secretary Sarah Sanders told reporters.

Sanders said the administration is "going to keep working with [Rubio] until we get the job done." Though she declined to say whether Trump endorses a more substantial child tax credit.

"Right now, we're going to focus on letting some of the Senate move forward in the progression of their conversations," Sanders added.

Rubio joined forces with Utah Sen. Mike Lee earlier this month to introduce an amendment that would have raised the corporate tax rate to 20.94 percent to pay for making the child tax credit refundable against payroll taxes. The amendment failed 29-71 in the Senate.

"20.94% Corp. rate to pay for tax cut for working family making $40k was anti-growth but 21% to cut tax for couples making $1 million is fine?" the Florida Republican tweeted on Tuesday, voicing his frustration with the current plan.

Rubio has called for making the $2,000 child tax credit included in the bill refundable against payroll taxes, a change that would benefit many low-income families who don't have income tax liability.

A representative for Rubio said he has told leadership that he won't vote for final passage unless the refundability of the credit is increased “in a meaningful way.”