Officials in Missouri's two largest cities filed a lawsuit Monday to block a new state law requiring voters to show photo identification.

Under the law, voters starting this November will need a photo ID issued by either the state of federal government, such as a driver's license, to cast a regular ballot. Those lacking IDs can cast provisional ballots, which would count if their signatures matched those on file with election authorities.

Republican Gov. Matt Blunt has praised the new law as a way to build public trust in elections.

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But the Democratic leaders in St. Louis and Kansas City who sued say the law violates a state constitutional provision against imposing costs on local governments without providing state funding. Their lawsuit seeks a permanent injunction blocking the law from being enforced and class-action status.

"Our overall concern is that the new law is going to leave people out who want to vote, who deserve to vote and who are qualified to vote," said Anthony Rothert, legal director of the American Civil Liberties Union of Eastern Missouri, whose group announced the lawsuit.

The lawsuit says implementing the new law would cost the Kansas City area's Jackson County alone $470,000 to mail notices to voters and add the extra equipment and Election Day staffing and training.

Republican state Sen. Delbert Scott, who sponsored the legislation, said election officials already send out voter cards and the law provides for free photo IDs that voters can obtain before Election Day.

"We anticipated a lawsuit. I think they're struggling for an issue," he said.

A federal judge last week blocked the state of Georgia from enforcing its new voter ID law this year. U.S. District Judge Harold Murphy said the Georgia photo ID requirement discriminated against people who don't have driver's licenses, passports or other government identification.