Commissioner Ray Kelly said New York could learn from London's so-called "ring of steel", a security and surveillance cordon which surrounds the city with concrete barriers, checkpoints and thousands of video cameras.

The NYPD wants to track every vehicle that enters Manhattan to strengthen New York's protection against a potential terror attack and officers have travelled to London to see the security measures in place there.

"We've asked them to look at the so-called ring of steel and we can learn from that," Mr Kelly said.

Mr Kelly and his command staff have been urging the creation of a London-style surveillance system for New York's financial district for months.

It would rely on licence plate readers, movable roadblocks and 3,000 public and private security cameras all linked to a security co-ordination centre, the New York Times reported.

Data on each vehicle -- its time-stamped image, licence plate imprint and radiological signature -- would be sent to a command centre in Lower Manhattan, where it would be indexed and stored for at least a month.

NYPD spokesman Paul Browne said the 90 million US dollar (£47.7m) Lower Manhattan initiative was expected to be in place by 2010.

"Our main objective would be to, through intelligence, find out about a plot before it ever got to a stage where a nuclear device or a dirty bomb was coming our way," he said.

But New York's plan, Operation Sentinel, would also involve capturing photographs of the licence plates of vehicles entering the city via all bridges and tunnels, and sensors would also detect the presence of any radioactivity.