The insurance company, Swiss Re, says it faces an after-tax burden of around SFr2 billion ($1.25 billion) after last week's suicide attacks on the United States. The company had previously forecast payouts of around SFr1.2 billion.
A company statement added that it was still undecided how and to what extent large loss reserves would be used to cover the amount. The estimate corresponds to around two thirds of the firm's annual profit last year.
It noted that it has reserves of about SFr2.5 billion to absorb such large losses. Swiss Re's share price dropped 6,62 per cent on the news to close Thursday's trading session at SFr134.
Meanwhile, the world's biggest reinsurance company, Munich Re, said it expected charges of around SFr3 billion as a result of the attacks.
Analysts have estimated that the insurance businesses could face claims of up to $15 billion as a result of the attacks in New York and Washington.
swissinfo with agencies