American insurers have reported subdued half-year profits as bad weather and volatile financial markets combine to put the squeeze on the bottom line.

WR Berkley, Liberty Mutual and Chubb last week reported modest results for the first half compared to the same period last year.

WR Berkley collected $US268.7 million ($282 million) in net profit, a 29% dip from the prior period, while the combined ratio reflected the tough trading as it increased from 87.7% to 91.7%.

Berkley paid $US23 million ($24 million) more in claims during the period than last year while profit from investments slid $US36 million ($38 million).

Liberty Mutual meanwhile banked a first-half profit of $US660 million ($693 million), a 4.2% decline despite a 12% increase in net written premium.

The insurer had a combined ratio of 101.3%, against 100.6% in the prior corresponding period.

Chubb incurred a 34% slide in profit to $US469 million ($492 million), despite a 4% increase in property/casualty investment income. The combined ratio was 88.5%, up from 82.7%.