WASHINGTON — When the next generations of $5, $10, $20, and $50 bills roll off the presses, there should be some way for blind people to tell them apart, a federal judge said today.

U.S. District Judge James Robertson said he would not allow the Treasury Department to go at its own pace as it complies with a May ruling that American paper money discriminates against the blind.

Treasury officials have hired a contractor to investigate ways to help the blind differentiate between bills, perhaps by printing different sizes or including raised numbers. Government attorneys urged the judge to let that process play out and not interfere with anti-counterfeiting redesigns that are already in process.

Judge Robertson was not persuaded.

“The Treasury Department is not going to just conduct this on its own schedule and its own terms. Let that be clear,” he said.

Judge Robertson ordered attorneys for the government to meet with the American Council of the Blind, which brought the lawsuit, and come up with a schedule that requires changes in the next generation of bills.

The next $100 design could be printed as early as this fall and Robertson said those bills won’t be affected. But subsequent designs should be able to solve the problem, the judge said.

Government lawyers said they plan to argue that Robertson does not have the authority to interfere with the Treasury’s printing responsibilities.

The judge said he’d consider the argument but quipped that, if he didn’t have authority to require changes, how was he supposed to enforce the ruling? What would the court order say, he asked, “Go out and have a good time? We’ll see you when it’s all over?”