NEW YORK -- While World Trade Center leaseholder Larry Silverstein was celebrating his courtroom victory over his insurers, experts on Tuesday were already debating its impact on the industry _ saying it could drive up rates for some businesses and force insurers to rewrite policies.

A federal court jury in Manhattan on Monday found that the attack on the World Trade Center was two events for insurance purposes. That means, barring a successful appeal, Silverstein will get another $1.1 billion for rebuilding at the trade center site.

"It could cause premiums to be re-evaluated and raised," said Dick Poppa, president of the Independent Insurance Agents and Brokers of New York. "Whenever you throw anything into the mix that diminishes insurers' ability to predict their loss, it is going to have some impact on pricing. But I don't think it's going to have a major effect."

But John Sarich, industry marketing manager for insurance for Costa Mesa, Calif.-based FileNet, predicted that "there's going to be some long-term effect on the industry in terms of policies and coverage. ... It probably won't affect the average homeowner but it's going to affect business and it's definitely going to affect big business."

Monday's verdict, after 11 days of jury deliberations, represents a big victory for Silverstein. The verdict doubles Silverstein's $1.1 billion payout from nine of his insurers, for a total of up to $4.6 billion.

Silverstein had insured the twin towers for $3.5 billion, and he sought a double payout of $7 billion based on the theory that the two planes that destroyed the two towers were two events.

The developer lost a bid to convince a previous jury that insurers holding the bulk of the coverage were not bound by an insurance document defining the attack as one event. The nine insurers affected by Monday's verdict had not used that wording.

Poppa said the ruling might cause insurers to change the definition of the word "occurrence" in their policies.

"This is just going to cause companies to take a second look and make sure that they're comfortable with their definition," he said.

Several major insurers issued statements downplaying the affect the decision would have on their bottom line.

St. Paul Travelers, one of the insurance companies in the case, said the decision, "taking into account the company's reserve position and reinsurance, will be immaterial to the company."

Hartford, which was not among the trade center's insurers, said the verdict "will not have a material impact on The Hartford."

Silverstein has said he will appeal the earlier ruling that went against him, and the insurers are expected to appeal Monday's verdict. A three-person appraisal panel will determine the damages at the trade center and how much each company must pay.

Regardless of the insurance payout, Silverstein and redevelopment officials have promised to rebuild the trade center complex in the next decade, including 10 million square feet of office space, a memorial and cultural buildings.

But Silverstein is already building 7 World Trade Center just north of the main trade center site with no tenants committed to it, and the verdict should give him some much-needed cash to build the remaining trade center commercial buildings while he waits for the sagging real estate market to pick up.

"If he had lost, that ground may have lain fallow for quite a long period of time," said
M. Myers Mermel, chief executive of the real estate brokerage company TenantWise. "It could have turned a 10-year project into a 15-year project."