London--The WPP Group plc advertising empire confirmed Monday that it has offered about $634 million for Tempus Group plc, tossing a monkey wrench into the plans of rival Havas Advertising SA to take over Tempus. WPP's cash offer of $8.05 per share is 3% higher than the bid made in July by France's Havas, which said it was considering its position and urged Tempus shareholders to take no action in the meantime. The counteroffer made by WPP will be open for at least 21 days from today. The deal for Tempus will further fuel what has been the rapid consolidation of the global advertising industry for the last decade or so, with fewer players controlling more marketing and communications. A WPP spokesman said his company hasn't decided what to do if Havas, which initially agreed to pay $7.84 per share for Tempus, makes a counteroffer. WPP's agencies, including Ogilvy & Mather, J. Walter Thompson and Young & Rubicam, handle some of the most prestigious advertising accounts in the world, such as AT&T Corp., Sony Corp. and IBM Corp. WPP already owns a 22% stake in Tempus. Top clients of Tempus subsidiary agencies CIA Worldwide, Outrider North America, Added Value and BrownKSDP include Coca-Cola Co., General Motors Corp., Prudential Insurance Co. and Eastman Kodak Co. WPP wants to fold Tempus' media and planning business, CIA, into its media unit, The Media Edge. Tempus chairman Chris Ingram would be invited to become co-chairman of WPP's investment division, Group MindShare Edge. In early morning trading overseas, WPP shares were trading 1% higher at $9.71 on the London Stock Exchange. Tempus' shares were 0.2% lower at $8.43. In a statement today to the London Stock Exchange, Tempus said that it "proposes to hold discussions, through its advisers, with each of Havas Advertising and WPP in order to determine the best eventual outcome for Tempus shareholders."