WASHINGTON – A group of U.S. senators, including Maine’s Olympia Snowe, called a May 11 deadline for compliance with federal Real ID rules “arbitrary and ineffective,” and asked the Department of Homeland Security to exempt states from it.

Homeland Security shot right back: “Perhaps these senators neglected to read the law that Congress passed, which actually set the date,” said agency spokesman Russ Knocke.

Maine, Montana, South Carolina and New Hampshire are the only states that so far have refused to seek an extension to identification rules by March 31, which Homeland Security says would be good enough at this point to comply with the May 11 deadline.

The agency said residents from noncompliant states could face extra screenings at airports and federal buildings.

Snowe, a Republican, joined Sens. John Sununu, R-N.H., Max Baucus and Jon Tester, both Montana Democrats, and Daniel Akaka, D-Hawaii, in sending a letter Wednesday to Homeland Security Secretary Michael Chertoff. It asked him to scrap the deadline or answer their questions about the process.

“It is our position that this deadline is both arbitrary and ineffective and imposes unnecessary burdens on all parties without enhancing our national security,” the senators wrote. “Furthermore, the department has not taken the steps necessary to implement this deadline effectively. We therefore respectfully request you exempt all 50 States from the May 11, 2008, deadline.”