Ivanka Trump on Wednesday stood with congressional Republicans to call for an increase in the child tax credit, as the GOP gears up to introduce and pass a tax reform bill.

"As wages have stagnated the costs of raising a family have grown, exponentially," Trump said as she stood with lawmakers to promote a larger child tax credit.

Trump attended the event only briefly, after which Republicans called for a boost to at least $2,000. Florida Sen. Marco Rubio said that the credit must be raised from $1,000 today to at least more than $1,800 simply to replace the value that has been eroded since the last time the credit was changed in 2003, and to make up for the loss of other breaks eliminated in the GOP framework for taxes.

A $2,000 credit is "actually not a very negotiable number because anything less than that doesn't really achieve the goal," Rubio said. He also said the credit must be made refundable against payroll taxes so that families that don't have income tax liability are still able to claim benefits.

Those demands would add to the fiscal costs of the GOP tax plan, and could require other parts of the tax bill to be scaled back.

The GOP framework called for increasing the credit and making it available to more families, but didn't specify an amount and said that only the first $1,000 would be refundable. The administration and congressional Republicans have maintained that the expansion of the credit will help ensure that middle-class families don't see tax hikes because of the tax bill.

Despite Rubio's demand, he and other Republicans who appeared with Ivanka Trump said that they didn't have a commitment to increase the credit to near $2,000 yet.

Sen. Tim Scott of South Carolina said that forming the tax bill is a "dynamic process," and that the child tax credit provision would be negotiated as the bill was written.

Nevertheless, Sen. Mike Lee of Utah projected optimism. "We need to get this done, and in the coming weeks I expect we will," he said.

The group also included Sens. Dean Heller of Nevada and Shelley Moore Capito of West Virginia, and Reps. Kristi Noem of South Dakota, Claudia Tenney of New York, Martha Roby of Alabama, and Kevin Yoder of Kansas.