Italian Premier Romano Prodi is under pressure to block the plan to set up the biggest American military base outside the United States on Italian territory, Italian News Agency ANSA said on Friday.
The weekly magazine L'Espresso revealed the controversial project in its latest edition which hit newsstands on Friday.
It said the US administration had obtained permission from the previous Italian government led by Silvio Berlusconi to build the new base in the northern city of Vicenza.
Vicenza already hosts an American military base where 6,000 troops are stationed.
More than 300 million dollars had already been released for 2007 for the construction of new barracks and other buildings.
The entire investment would amount to 1 billion dollars with work due to be completed by 2010, the weekly said.
Several parties in Prodi's nine-way governing coalition immediately called on the premier to halt the project.
Hard leftists and pacifists, who have already crossed swords with Prodi over the continued deployment of Italian troops in Afghanistan, were particularly alarmed and demanded clarification from Italian Defense Minister Arturo Parisi and Foreign Minister Massimo D'Alema.
Elettra Deiana of the Communist Refoundation Party said "this is such a huge project with such strategic implications that this government could never approve it".
The Italian Communists' Party and the Green party called for "clear and decisive" government action to prevent the plan going through.
The parties stressed that agreement had only just been reached on the closure of a controversial US nuclear submarine base in Sardinia.
The Democratic Left, the largest party in the coalition, also expressed concern about the Vicenza project.
Democratic Left Senator Silvana Pisa said that "they are closing military bases and installations across Europe. Only Italy and Bulgaria are doing the opposite".
The UDEUR, a centrist party in the four-month-old Prodi government, expressed opposition to the project but said it could be difficult to halt.
"The problem is that the Italo-American accord has already passed the final approval stage with the assent of the local authorities in Vicenza," it said.
(Xinhua News Agency September 23, 2006)