A Swiss reinsurer is saying “non” to an unsolicited offer from a French reinsurer.

Converium Holding Ltd., Zug, Switzerland, has rejected a takeover bid with a value of about $2.5 billion from SCOR, Paris.

The SCOR bid “fundamentally fails to recognize the value of Converium’s franchise and growth prospects” and is not in the best interests of Converium shareholders, Converium says in a statement.

Converium’s board believes the company can achieve a sustainable 14% annual return on equity by 2009, the company says.

SCOR says it already has acquired 32.9% of Converium’s shares.

“SCOR is fully convinced that the combination of Converium and SCOR is in the best interests of both companies, their shareholders and stakeholders,” SCOR says in its statement.

Analysts in the London office of Standard & Poor’s say SCOR’s move could open the doors for other unsolicited takeover proposals.

Although Scor and Converium are best known as property-casualty reinsurers, life reinsurance accounted for about 34% of 2005 net operating income at Scor and about 17% of 2005 total net premiums written at Converium, according to company figures.

Jim Connolly contributed information to this article.