The federal government has agreed to let Florida use a law enforcement database to challenge people's right to vote if they are suspected of not being U.S. citizens.

The agreement comes in a letter to Florida Gov. Rick Scott's administration that was obtained by The Associated Press.

The agreement grants the state access to a list of resident noncitizens maintained by the Department of Homeland Security. The Obama administration had denied Florida's request for months, but relented after a judge ruled in the state's favor in a related voter-purge matter.

Voting rights groups have expressed alarm about using such data for a purpose not originally intended -- purging voter lists of ineligible people. They say purges less than four months before the election might leave insufficient time to correct mistakes.