A potential multibillion pound merger between defence giant BAE Systems and Airbus aircraft manufacturer EADS has come under further pressure after a major shareholder demanded a better deal.
French media tycoon Arnaud Lagardere, who is EADS chairman and whose company Lagardere owns a 7.5% stake, wants better terms for French controlling shareholders.
And German automotive company Daimler, which owns a 22.5% stake in EADS, though only 15% directly, is also thought to share many of Lagardere's concerns.
Lagardere urged EADS management to complete "without delay, the indispensable re-examination of the project to combine EADS and BAE, to better take into account the interest of all the French controlling shareholders of EADS".
EADS chief executive Tom Enders is understood to have held talks with the billionaire in a bid to salvage the deal, which would create the world's biggest aerospace company with a market value of around 50 billion US dollars (£31 billion).
The obstacle comes after Mr Enders and BAE chief executive Ian King issued a plea for political support for the proposed merger and said it would create a global company that would be more than the sum of its parts. The deal will require the approval of the British, French and German governments if it is to go ahead, while the United States is understood to be taking a close interest in the deal because of BAE's involvement in sensitive US defence projects.
UK unions fear that the move will trigger thousands of job cuts, while the British government is expected to block the deal if it saw the French and German governments take stake above 9% in the new combined entity.
Speaking at the Royal Academy of Engineering, as reported in the Daily Telegraph, Mr Enders said: "It's absolutely not surprising that some shareholders are concerned about the benefits and their returns.
However, Mr Enders also warned the merger talks need to press ahead because of the uncertainty for workers and investors. He said: "We cannot go on for much longer." In a joint article published by the Financial Times, German paper Die Suddeutsche Zeitung and French paper Le Monde, Mr King and Mr Enders attempted to reassure politicians' concerns.
They said: "BAE Systems and EADS are both strong businesses with clearly defined strategies that have enabled them to make progress in the last five years, and which would take them forward as independent companies."