UPDATE 1-United Internet says won't fold in freenet poker

(Adds CEO comment, share price, Freenet reaction)

FRANKFURT, May 7 (Reuters) - United Internet (UI) (UTDI.DE: Quote, Profile, Research, Stock Buzz), Germany's second-largest Internet service provider, is seeking a court order to block domestic rival freenet's plan to acquire mobile firm Debitel, UI's chief executive said on Wednesday.

United Internet, a major shareholder in freenet (FNTG.DE: Quote, Profile, Research, Stock Buzz), is fiercely opposed to the plan, arguing it is not in the interest of a majority of shareholders, but freenet agreed last week to buy the larger Debitel for 1.63 billion euros.

Having failed to block the deal with a sweetened bid for freenet, United Internet has now filed for an injunction to stop freenet from issuing new shares, which Debitel's owner, private equity firm Permira, is due to receive in the sale.

United Internet CEO Ralph Dommermuth told Reuters in an interview on Wednesday a court hearing on May 22 will rule whether freenet has the right to issue new shares.

Freenet said it assumes United Internet's bid for a court injunction will not succeed.

Dommermuth also said United Internet will also seek a court order allowing it to call a freenet shareholder meeting.

"It's May and freenet has yet to invite shareholders for its annual general meeting, that's a breach of stock corporation law," Dommermuth said.

United Internet had wanted to split up freenet, keeping the Internet business and letting its joint venture partner Drillisch AG (DRIG.DE: Quote, Profile, Research, Stock Buzz) have the mobile telecoms part.