* Broadcasters seek court ruling before required to post ad contracts
* Say new FCC rules would cause broadcasters "irreparable harm"
* Say broadcasters could lose millions in ad revenue
By Jasmin Melvin
WASHINGTON, July 11 (Reuters) - The National Association of Broadcasters has asked a federal appeals court to prevent new rules from taking effect Aug. 2 that would force broadcasters to publish political advertising contracts online.
The Federal Communications Commission adopted the rules in April in an effort to provide insight on campaign spending ahead of November's congressional and presidential elections. The rules would reveal who is paying for political campaign ads and just how much they are shelling out.
The NAB filed an emergency motion with the U.S. Federal Court of Appeals for the District of Columbia Circuit on Tuesday to block the rules from taking effect until the judicial review is over.
The group said its members stand to lose millions of dollars in ad revenue.
"Non-broadcast competitors will be able to determine in a matter of seconds exactly what prices local broadcast stations are charging for specific spots," NAB said in its court filing.
"As a result, they will acquire an unfair advantage over broadcasters in the competition for political and commercial advertising, just as a poker player who is able to peak at an opponent's hand acquires an unfair advantage in a poker game," it added.
The trade group said the FCC's disregard of the competitive harm of leaving broadcasters' cable and Internet competitors unaffected by the new rules would cause the industry irreparable harm.
TV stations have been making public their records of campaign advertising buys and other community-related issues since 1938 as part of their public interest obligation.
Obtaining these files is currently a time-consuming, labor-intensive task, requiring multiple trips to TV station studios and money to pay for photocopies of the documents.
The new data format, to come initially from the four biggest TV broadcasters in the top 50 media markets, includes detailed information on who paid for political ads, key personnel of the groups buying ads, when political ads aired and rejections of requests to buy air time.
The four biggest broadcasters are ABC, operated by Walt Disney Co, CBS Corp, News Corp's Fox, and NBC, controlled by Comcast Corp.
The top broadcasters would have to upload their political files to a database hosted on the FCC's website beginning Aug.2 if the court does not grant the NAB's motion.
The trade group previously filed a petition for review in April with the D.C. appeals court, charging that the rules are arbitrary, capricious, violate free speech protections in the U.S. Constitution and go beyond the FCC's statutory authority.
The FCC declined to comment.