(Reuters) - An atheist group has sued Kansas City, Missouri, charging that plans to use $65,000 in tourism tax dollars to assist in an upcoming Baptist convention violates guarantees in the U.S. Constitution separating church and state.

The lawsuit, filed on Friday in U.S. District Court by American Atheists Inc against officials including Kansas City Mayor Sly James, asks a federal judge to block the city from spending taxpayer dollars to support the event.

It contends that using tax dollars to help Modest Miles Ministries Inc, prepare for the National Baptist Convention USA Inc, would advance a religious purpose in violation of American Atheists' right to be of state-supported religion, as provided for under the "establishment clause of the First Amendment of the U.S. Constitution.

In April, the city approved to pay $65,000 in municipal funds from the Neighborhood Tourist Development Fund to the ministry to help transportation costs, the lawsuit said. The conventions is scheduled to be held Sept. 5-9 in Kansas City.

Kansas City spokesman Chris Hernandez declined to comment on the pending lawsuit. But a contact has not been signed for the funds to be released, and standard contract language excludes religious use of any funding, Hernandez said.

About 10,000 people are expected to attend the convention, which was previously held in the city in 2010, 2003 and 1998, the Kansas City Star reported.

(Reporting by Justin Madden in Chicago; Editing by Scott Malone and Alan Crosby)