Lawmakers working to craft a new comprehensive immigration bill have settled on a way to prevent employers from hiring illegal immigrants: a national biometric identification card all American workers would eventually be required to obtain.

Under the potentially controversial plan still taking shape in the Senate, all legal U.S. workers, including citizens and immigrants, would be issued an ID card with embedded information, such as fingerprints, to tie the card to the worker.

The ID card plan is one of several steps advocates of an immigration overhaul are taking to address concerns that have defeated similar bills in the past.

The uphill effort to pass a bill is being led by Sens. Chuck Schumer (D., N.Y.) and Lindsey Graham (R., S.C.), who plan to meet with President Barack Obama as soon as this week to update him on their work. An administration official said the White House had no position on the biometric card.

"It's the nub of solving the immigration dilemma politically speaking," Mr. Schumer said in an interview. The card, he said, would directly answer concerns that after legislation is signed, another wave of illegal immigrants would arrive. "If you say they can't get a job when they come here, you'll stop it."