"We would have to consider any new bid which is made," he said. "We would reconsider any small, medium or large change and our reaction would be whether the change is important enough to really make a difference." He added that an appropriate price would top 300 euros.
Mr Esser, who said shareholders have "overwhelmingly" supported his rejection of the Vodafone offer, conceded that "it is too early to say what shareholders want." He added that accepting Vodafone's bid would be "almost the most stupid thing we could do".
The German chief executive's road show to visit Mannesmann shareholders is expected to last another fortnight, but could extend into the new year. Under German law, Mannesmann directors may present new information until Vodafone presents its formal offer document.
But that opening allowing Mr Esser to continue the fight back could close sooner than expected, should a Dusseldorf court back a shareholders group that has filed an injunction against Mannesmann's board. The group claims the board's opposition to Vodafone's offer is against their interests. The court could make a decision today or schedule a hearing for next week.
Yesterday Mr Esser reiterated his key themes in opposition to the offer, the world's biggest. These include Mannesmann's expected 30 per cent plus operating cash flow growth through 2003; its better strategic position due to controlling its main business units; and its combination of wireless and fixed-line networks.
Chris Gent, the Vodafone chief executive, said: "The question that Mannesmann consistently fails to address is what it can do better by itself than with Vodafone AirTouch." Vodafone's stock closed down 4.5 per cent at 312p, while Mannesmann ended down 3.4 per cent at 231.75 euros.