WASHINGTON – The Senate tax proposal would raise the child tax credit to $1,650 – only $50 more than the House version – denying Sen. Marco Rubio and allies who say it must increase much more.

Leaked details ahead of the official unveiling came as Rubio continued an aggressive pitch to double the current $1,000 credit. Rubio has said anything less will hurt families and has suggested he could vote against the bill.

Rubio's office has not responded to questions about the tax credit. He once talked about $2,500, but had settled on a lower amount. Senate Democrats say even $2,000 in inadequate.

UPDATE: Rubio responds on Twitter.

Rubio appeared on Fox News earlier today and hinted at disappointment.

"I expect it'll be better than the House position. And we'll keep working on it. Look, if I don't like it, I can file an amendment on the Senate floor. And I am pretty confident I have the votes.

"And, by the way, $2,000 is not some number out of the air. That is the point in which you are giving a tax cut to people who will have… two, three, four children, are raising a family, are working because you can't get this if you are not working.

"Here's what I can tell you: it cannot be that it is more lucrative to not work and raise four kids with the government benefits that come with that, than it is to take a job for $35,000 a year. That can't be, and our tax code should not encourage that."

One analysis of the House bill found that 42 percent of children in working families in Florida could be left out.