SUN PRAIRIE, Wis.—Less than a month after QBE Insurance Group Ltd. said it would buy Praetorian Financial Group Inc., the Australian insurer has made another big U.S. acquisition, agreeing to purchase Winterthur US Holdings from AXA S.A. for $1.16 billion.

Sun Prairie, Wis.-based Winterthur US, which operates primarily under the names of General Casualty and Unigard, writes small and midsize commercial and personal property/casualty coverages through independent agents in 33 states. Its gross premium volume for 2006 is expected to reach $1.48 billion, according to New York-based Standard & Poor's Corp.

According to QBE, 64% of Winterthur US' business is commercial. Commercial coverages written by its units include general and professional liability, workers compensation, property, marine and commercial auto.

The latest acquisition completes QBE's strategy of building four major streams of business in the Americas: specialty insurance programs, property and casualty insurance in regional markets, reinsurance and Latin America, the Sydney-based insurer said in a statement.

QBE expects to finalize the acquisitions of both Winterthur and New York-based Praetorian, a specialty insurance firm it purchased for $800 million, in the second quarter of 2007, pending regulatory approvals. In other recent U.S. deals, QBE bought National Farmers Union Property & Casualty Co. in 2005 and One Beacon Agriculture early last year.

Tim Kenny, president and CEO of QBE's New York-based Americas division, said the U.S. acquisitions total will represent slightly less than 40% of the Australian company's total gross premiums.

In the Americas alone, gross premiums are expected to reach around $4.6 billion, Mr. Kenny said. According to QBE's financial statements for 2005, gross premiums written for the Americas Division were just over $1 billion.

Mr. Kenny said his division is not finished growing but will concentrate on areas outside the United States.

"This is our last acquisition (in the United States), for now," he said. "Our focus right now is in Latin America."

QBE already owns companies in Argentina, Brazil and Colombia and is looking to expand those operations and create or acquire new ones in Mexico and Chile, he said.

In a Jan. 5 statement following the purchase of Winterthur US, S&P's said QBE's A- financial strength rating would not be changed.

The New York-based rating agency said the latest acquisition "would enhance QBE's business profile in the U.S., providing it not only a larger scale of operations, but also a strong geographical presence and a sound distribution platform."

"Winterthur US has a sound business position in the U.S. with good brands, and a well-established infrastructure and distribution platform in commercial and personal business lines," according to the statement by S&P, which does not rate Winterthur US.