A US jury will this week decide the first round of a $7 billion (£3.9 million) legal battle between Larry Silverstein, the World Trade Centre leaseholder, and his property insurers.

A group of 13 insurers, including a Lloyd’s of London syndicate and Swiss Re, claim that they owe $3.5 billion for the destruction of the World Trade Centre in the terrorist attacks of September 11, 2001.

However, Mr Silverstein and the site’s owner, the Port Authority of New York and New Jersey, claim they are owed $7 billion, double the policy value, because the destruction of the twin towers came after two aircraft crashed into the towers.

The insurers maintain that the terrorist atrocity was a single continuous event.

The jury in the trial, which began more than two months ago, is expected to start its deliberations today. The initial part of the case revolved around the insurance policies covering the World Trade Centre.

The insurers argued that they provided cover under a policy form known as “Wilprop”, issued by the insurance broker Willis Group. The court has already ruled that under the Wilprop form the attacks on the World Trade Centre were one occurrence — not two events as Mr Silverstein claimed.

Mr Silverstein’s lawyers said that the coverage was issued under a separate policy document, which leaves open the definition of the word “occurrence”.

Regardless of the verdict this week, the insurers are likely to be plunged into a second court battle that will consider how much policies written under forms other than Wilprop will be required to pay out. A third trial, likely to begin next year, will determine how much each insurer pays.

The trials will be crucial in determining how much money is available to rebuild the site, as Mr Silverstein is expected to foot most of the bill. Last month the developer said he expected the redevelopment to cost at least $12 billion. The US Government is expected to contribute $5 billion to the cost of rebuilding the subway station on the site.

THE COSTS

• $12 billion: Cost of rebuilding the World Trade Centre

• $5 billion: Cash from US Government

• $7 billion: Insurance payout demanded by Larry Silverstein

• $3.5 billion: Amount the insurers are willing to pay out

• $1.5 bn (1966-73): The original cost of building the WTC