Officials and advocates packed Mayor Vincent Gray’s event in May unveiling the license bill. (Mike DeBonis/The Washington Post)

The D.C. Council was set to take a final vote Tuesday on a bill allowing illegal immigrants to apply for District driver’s licenses for the first time. But the vote was delayed at least two weeks after the member shepherding the bill through the council said details remained to be worked out with federal authorities.

Mary M. Cheh (D-Ward 3) said the two-week delay would allow the language of the bill to be perfected, in part to allay concerns that the measure could run afoul of federal law. Allowing undocumented residents to hold licenses indistinguishable from those held by legal residents could run afoul of the yet-to-be-implemented REAL ID Act, which sets tough standards for state ID cards.

In an interview Monday, Cheh said she has met with high-ranking officials at the Department of Homeland Security who, while not taking an official position on the legislation, raised some concerns with it.

Some states that have moved to offer licenses to illegal immigrants, including Maryland, have used markings indicating such licenses are “not for federal identification purposes” or something similar. But immigrant advocates have opposed doing that in the District, calling it a  “scarlet letter” that would serve to alert law enforcement that the person bearing the license is in fact undocumented.

The advocates also suggest that the federal government has no plans to implement the REAL ID Act, which was passed in 2005 but has not been enforced in any significant way. But Cheh said the Homeland Security officials indicated that that may change in the coming weeks: “They say, ‘We’re really doing it, we’re really doing it.’ ”

Cheh said she suggested to the feds that the District might issue indistinguishable licenses to immigrants but have them expire within a year, allowing more flexibility if federal policy changes. “They didn’t like that,” she said, “because once that gets launches they think pulling that back would be tricky.” Officials at Homeland Security headquarters could not be reached Tuesday due to the federal shutdown.

As a Plan B, Cheh says, she proposed a less conspicuous marking on the licenses issued to the undocumented — such as a different-colored border. “They’re going to get back to me about that,” she said.

In any case, advocates are upset about the delay and Cheh’s ongoing discussions with federal officials.

Jaime Contreras, capital area director for Service Employees International Union 32BJ, said his group is “disappointed that Cheh did not consult with advocates before delaying the bill and appears to be only listening to the feds” in a statement released through a spokeswoman.

The union represents over 17,000 janitors and security officers in the District, most of whom are immigrants, and has pushed mightily for a single license for all applicants regardless of residency status