MILAN - The much-debated plan to build a bridge linking Messina on the island of Sicily with the toe of the Italian boot moved a step closer to realization on Wednesday after the company organizing the project awarded a 3.88 billion construction contract.

Impregilo, Italy's largest construction company, heads the group that won the contract for what would be the longest suspension bridge in the world at 3.7 kilometers, or 2.3 miles. Including inflation and financing costs, the final bill is projected to be about 6 billion, or $7.2 billion, according to government-owned Stretto di Messina, the company that picked Impregilo and is in charge of the design and financing of the project as well as eventual operation and management of the bridge.

The plan for the bridge, dreamed of in Roman times and discussed with varying degrees of seriousness by politicians over the past 30 years, has solicited impassioned pleas from both supporters and detractors. The former say it will help Italy's impoverished south by kick-starting the region's economy and improving its decaying infrastructure while the latter contend it is a waste of government money, much of which they say will end up in the hands of organized crime.

Construction would come at a time when the Italian economy is emerging from its second recession in as many years into an uncertain future. The government, the World Bank and independent economists forecast anemic growth at best for Italy's economy for the next three years.

Prime Minister Silvio Berlusconi has vigorously supported the project and exploited the issue in his 2001 campaign.

While environmental groups have promised to fight the bridge's construction, most seem convinced that with or without their opposition, a project this big and this expensive will never be realized.

"It is clear that this bridge will never be built, but the government wants to begin the work as soon as possible so they can tell everybody what a good job they are doing," Roberto Della Seta, chairman of the environmental group, Legambiente, said in an interview.

"By the time this project is stopped, loads of money will have been wasted," said Della Seta. "Building this bridge doesn't confront the real problem, which is that Sicily has a transport system from the Middle Ages that you'd have trouble finding anywhere else in Europe. This money should be spent elsewhere."

Though the government will not directly fund the bridge, all of Stretto di Messina's shareholders - a government holding company, the state-owned railroad and highway operators and the regions of Sicily and Calabria - are public entities.

Designs show the bridge itself to be very 21st Century. With a width of 60 meters, or 200 feet, it will be able to carry as many as 6,000 cars an hour and 200 trains a day on its six lanes and two-way rail tracks. There will be another two lanes reserved for service vehicles. The two towers holding up the bridge will rise about 395 meters above the water, making them taller than the Eiffel Tower in Paris.

But any progress on this mammoth project, which is scheduled to last six years, could grind to a halt in little more than half a year if Romano Prodi, the leader of the opposition coalition, wins election, as polls are predicting. He has already hinted as much, though with thousands of jobs potentially hanging in the balance, he has yet to take a definitive stand.

If it does get built, the bridge is designed to withstand an earthquake of a magnitude of 7.1. That, critics say, is hardly enough to guarantee the bridge would survive a major earthquake in what is one of Italy's most seismically active areas.

Impregilo's shares on the Italian stock exchange gained 5.2 cents, or 1.5 percent, to close at 3.52 on Wednesday, indicating that at least some people are betting the bridge will be built and that some companies are set to make a profit on its construction.