A group of Allegheny County residents and the national People for the American Way filed suit in U.S. District Court yesterday to block the county from switching to touch-screen voting machines and paper ballots for the May 16 primary election.

The group is seeking an injunction to require the county to continue using its lever machines instead of the iVotronic machines the county agreed to purchase last week from Election Systems & Software, or ES&S, for $11.9 million. The ES&S machines were the county's second choice after machines manufactured by Sequoia Voting Systems failed to pass state certification tests.

The lawsuit, with local community activist Celeste Taylor as the lead plaintiff, claims there isn't enough time to train poll workers and voters properly on the use of the new machines, and that the new machines are not fully accessible to voters with certain disabilities.

Two plaintiffs are people who use wheelchairs.

Counties across the country are expected to use new voting machines this year to meet the Help Americans Vote Act, or HAVA, which was passed after the problems in Florida in the 2000 presidential election.

Also yesterday, the county announced that ES&S will provide 2,628 of the iVotronics for the May primary, enough to have two in every precinct. The company will also provide an optical scan machine to read paper ballots cast in the primary, and will deliver all 4,700 iVotronics in time for November's general election.

In addition, the county unveiled plans to equip one of the two machines at each precinct with "sip and puff" technology, which allows disabled voters with restricted mobility to cast their ballots without assistance.

Also, each of the county's electronic voting machines will be modified to produce voter-verified paper audit trails. Both upgrades, however, require state certification.

Despite the modifications, Harry Litman, an attorney representing Ms. Taylor, said the primary goal of the lawsuit remains the same.

"None of it changes the basic point," he said. "It sounds like this just adds one more patch to a patchwork decision."

County officials did not return repeated calls for comment.

The decision to purchase the machines from ES&S only five weeks before the primary will cause major problems on May 16, said Elliot Mincberg, vice president and legal director of People for the American Way.

"It is a recipe for problems," Mr. Mincberg said. "We have seen over and over and over again that making this kind of decision at the last minute is bound to create problems that people don't anticipate."

The county cannot rush a decision that will affect thousands of voters for years to come, Mr. Litman said.

"We're trying to force the county to slow down, rethink [the decision] and give Allegheny County a chance to pick a set of machines that can be used for the next 40 years," he said. "We're going to have to live with these machines for a long time."

If the county is not in compliance with the federal law by the May primary, it could face legal action from the U.S. Justice Department, including the loss of a $12 million grant to be used to purchase the new machines and fund an educational campaign for voters and election workers.

That pressure from the federal government is forcing the county into a precarious position, Ms. Taylor said.

"I would hope that the [federal government] would chill out," she said. "They really need to realize what is happening here. Are we going to put a price tag on people's right to vote?"

County Chief Executive Dan Onorato has previously called the federal law "the biggest waste of federal money I've ever seen."

"We appreciate that the county is caught between a rock and a hard place," Mr. Litman said. "The ideal solution would be one that complies with HAVA and doesn't eliminate the federal funding.

"But if push comes to shove, the right to vote is too important to compromise for the federal money."

Defendants include Pennsylvania Secretary of State Pedro Cortes, Mr. Onorato, county Manager James Flynn, and senior officials at the Justice Department, who the lawsuit alleges have pressured the county to buy new machines by threatening to revoke the $12 million grant.