NEW ORLEANS – The Coast Guard plans to use dozens of buoys bobbing off U.S. coastlines from Maine to Alaska to extend the reach of a security system that monitors large vessels heading in and out of ports.

The buoys, from 9 to 39 feet across, already are in place, used by the National Oceanic and Atmospheric Administration to collect wind, temperature and wave data.

The weather service has agreed to let the Coast Guard add transmitters to about 70 buoys by 2007, said Jeff High, a director of the Coast Guard’s Maritime Domain Awareness Program in Washington, D.C.

The transmitters will connect to a communications network that this year began receiving signals from all large tankers, barges and cruise vessels heading in and out of major U.S. ports. To legally enter a U.S. port, each vessel must be equipped with a machine that automatically radios information – its cargo, crew list, recent ports of call – to the Coast Guard.

The buoys are intended to extend the network’s reach; the Guard now receives the automated data only when a vessel is within about 25 miles of a port. The floating transmitters will relay the information from hundreds of miles offshore, from the middle of Lake Superior and off coastlines from Alaska to Maine.

“They’re pretty well spread out, they’re essentially all around the coast, into the Atlantic and the Pacific,” High said.