Sen. Marco Rubio will have to fight for a doubling of the child tax credit he has aggressively pitched in recent weeks after House Republicans on Thursday unveiled a plan to increase it by only $600.

Rubio wants the $1,000 credit to rise to at least $2,000.

On Twitter, Rubio said the House plan falls short of what advocates, including President Trump, want.

“What if we do less like some are suggesting?” Rubio said Tuesday on the Senate floor. “Let’s just raise the tax credit to $500, but let’s not make it refundable against payroll tax. They’ll get a tax cut of about $263. And when you compare that to some of the tax cuts you’re going to see in other parts of this tax reform, I would say that’s not nearly enough. It’s certainly not enough to make a difference.

“But what if you do this: what if you double the value from $1,000 to $2,000 of the tax credit and you make it refundable towards payroll tax. That couple, with those two children, will have a tax cut of $1,263. Now that doesn’t solve all their problems, but it makes a difference.”