Democrats plan a child tax credit of up to $3,600 as part of their stimulus bill.

Top House Democrats are preparing to introduce legislation that would send up to $3,600 per child to millions of Americans, as lawmakers aim to change the tax code to target child poverty rates as part of President Biden’s sweeping $1.9 trillion stimulus package.

The proposal would expand the child tax credit to provide $3,600 per child younger than 6 and $3,000 per child up to 17 over the course of a year, phasing out the payments for Americans who make more than $75,000 and couples who make more than $150,000. The draft 22-page provision, reported earlier by The Washington Post and obtained by The New York Times, is expected to be formally introduced on Monday as lawmakers race to fill out the contours of Mr. Biden’s stimulus plan.

“The pandemic is driving families deeper and deeper into poverty, and it’s devastating,” said Representative Richard E. Neal of Massachusetts, the chairman of the Ways and Means Committee and one of the champions of the provision. “This money is going to be the difference in a roof over someone’s head or food on their table. This is how the tax code is supposed to work for those who need it most.”

The credits would be split into monthly payments from the Internal Revenue Service beginning in July, based on a person’s or family’s income in 2020. Although the proposed credit is only for a year, some Democrats said they would fight to make it permanent, a sweeping move that could reshape efforts to fight child poverty in America.

The one-year credit appears likely to garner enough support to be included in the stimulus package, but it will also have to clear a series of tough parliamentary hurdles because of the procedural maneuvers Democrats are using to muscle the stimulus package through, potentially without Republican support.

With House Democratic leadership aiming to have the stimulus legislation approved on the chamber floor by the end of the month, Congress moved last week to fast-track Mr. Biden’s stimulus plan even as details of the legislation were still being worked out. Buoyed by support from Democrats in both chambers and a lackluster January jobs report, Mr. Biden has warned that he intends to move ahead with his plan whether or not Republicans support it.