Tempus said the talks were to determine the best eventual outcome for Tempus shareholders.
According to a Tempus statement, "At that time, the board of Tempus will make a recommendation to its shareholders. In the meantime, the board is withdrawing its recommendation to accept the cash offer of 541 pence per share from Havas Advertising and shareholders are advised to take no action pending further clarification."
WPP bid 555p this morning, valuing Tempus at around £437m, compared with the French company Havas's 541p bid, which values the media-buying group at £425m.
Havas has said that it plans to weight its options before making a response. However, those close to the group say that the French group could bounce back with a counter-bid tomorrow.