A key group of Karstadt's senior debt holders have agreed to the takeover plan for insolvent German retailer by billionaire investor Nicholas Berggruen, ahead of a midnight deadline, a spokesman for Berggruen's holding company said Thursday.

The senior tranche B debtholders, which are part of a real estate investment vehicle which owns Karstadt properties, gave "100% approval" for Berggruen's plan at a meeting in London Thursday, the spokesman said.

A further group of mezzanine debt holders are expected to approve Berggruen's takeover plan before the end of Thursday. A final decision to confirm the Karstadt deal will be determined by an Essen-court Friday.

Berggruen won a tentative deal to acquire Karstadt in June, which was dependent on reaching an agreement with creditors on issues including reductions in property rents and a revised lease agreement.

The German-American investor has spent months haggling over the terms with creditors including Germany's Valovis Bank and Highstreet, a real estate consortium led by Goldman Sachs Group Inc.

-By William Launder, Dow Jones Newswires; +49(0)6929725515; william.launder@dowjones.com