HNA's 53 Swiss franc (39 pounds) per share cash offer was unanimously supported by the Swiss caterer's board.

While a rival bid was still possible, Gategroup Chairman Andreas Schmid said on a media conference call, the company was not actively seeking other offers.

HNA Chief Executive Adam Tan did not respond directly when asked whether the Chinese conglomerate would be willing to up its bid if another suitor made a bid. "We've already made a very attractive offer to the shareholders," Tan said.

(Reporting by Paul Arnold, Writing by Brenna Hughes Neghaiwi; Editing by Michael Shields)