Construction of the new Freedom Tower on the World Trade Centre site in New York will not be able to start if insurers continue to withhold payments promised to the developer.

Under new agreements with the leaseholder on the site, Larry Silverstein, the landowner, the Port Authority of New York, is entitled to $US962 million ($1.2 billion) of the $US4.6 billion ($6.2 billion) of insurance payouts directed towards the building of the Freedom Tower and another building on the site.

Mr Silverstein has asked New York officials to help him retrieve the funds from the insurers so he can meet deadlines for construction set out by the state.

The construction start deadline has already passed, but Mr Silverstein has pledged to keep the project on track once the funds have been received.