Ace has revealed plans to launch an offering to sell $300m (£186m) in shares.
In a statement Ace said the new share offering would be the first step in its plans to boost capital by up to $500m (£311m).
The preferred shares will be issued in the form of depositary shares, it said.
Ace said it expects to use the proceeds from the offering to make capital contributions to its subsidiaries and for "general corporate purposes".
Citigroup Global Markets and Merrill Lynch are acting as joint-book running managers for the offering.
