Mayor Rudolph Giuliani has the backing of the state's two U.S. senators for a $1 billion rail freight tunnel to link the city with the mainland, slashing its heavy reliance on truck deliveries.

Democrat Sen. Daniel Patrick Moynihan and Republican Sen. Alfonse D'Amato both vowed Washington would pick up a large part of the tab for the tunnel project, the first new crossing built for the city in more than 30 years.The city has turned to some of the experts who worked on the Channel Tunnel, the historic rail link between Britain and France, to carry out an engineering study that is expected to take 18 to 24 months to complete, and cost up to $4.5 million.

Preliminary plans call for the tunnel to connect Brooklyn and Newark, N.J., either directly, or via Staten Island.

The Republican mayor, who has blistered the Port Authority of New York & New Jersey for failure to build the tunnel - the reason the agency was created in the 1930s - said the link would save shippers from having to send rail freight on a 280-mile detour.

At present, cargo that comes in by rail from the south and southwest destined for New York City and Long Island must first travel north to Selkirk - a town just south of Albany and the only place freight trains can cross the Hudson - before it can be shipped back down to the city and points East.

Only 5 percent of the cargo sent to the city arrives by rail, a much lower rate than the national average of 26 percent, Mr. Giuliani said. Whereas, Mr. Moynihan estimated that around 50,000 trucks carry goods through the area per day.

The over-dependence on trucks costs the region $12 billion a year in congestion delays, said the mayor. He also cited wear and tear on roads and underground infrastructure as well as higher manufacturing costs. The port authority says it supports searching for better ways to move freight through the region.

As Congress on Monday took up a massive new transportation bill, Mr. Moynihan and Mr. D'Amato expressed confidence that financial aid for the tunnel would be forthcoming.

Edwards and Kelcey Engineers Inc. will conduct the study, which is expected to examine other options, including float bridges, and cover engineering drawings, the impact on the environment and the economy, and financial implementation.

Subcontractors will include Hatch Mott and McDonald, who designed the St. Clair River Railway tunnel that links Michigan and Canada, and also worked on the chunnel.