Asatsu-DK Inc.'s chief executive officer said he is determined to sever an alliance with top stockholder WPP PLC, seven months after the world's largest advertising agency called on share owners to vote him out.

CEO and President Shinichi Ueno said in an interview that the two-decade old WPP partnership is over and Asatsu-DK is looking for new tie-ups in the industry, the latest salvo in a battle re-ignited by Bain Capital LP's $1.3 billion bid to buy the company two weeks ago. The alliance with London-based WPP is finished, whether or not the Bain offer succeeds, Ueno, 63, said Wednesday.

Asatsu-DK is meeting with shareholders to make the case for the Bain offer, which would take the company private, end the WPP tie-up and ease the way for a restructure, Ueno said. Asatsu-DK has said WPP has made it more difficult to carry out a revamp that's needed to meet challenges from digital advertising offerings from giant rivals like Dentsu Inc. and from Facebook Inc. and Google.