The US military said Thursday it will close a major air base in Britain and withdraw from 14 other installations across Europe as part of a reorganization of forces to save money.

The "consolidation" will save the US government about $500 million a year and not diminish American military power, Pentagon officials said, but the move prompted disappointment in Britain and anger in Portugal over the potential economic effect of the scaled-back presence.

The closure of bases and various outposts over the next several years will likely reduce the current contingent of 67,000 American forces in Europe by only about 1,200 troops, a defense official told AFP.

Under the plan, US operations at RAF Mildenhall in Britain will end and 500 troops and civilians will be withdrawn from Portugal's Lajes Field in the Azores. Commanders concluded the Lajes air base was largely a relic from another era when aircraft on transatlantic flights needed to refuel or make emergency landings on their way to the European continent.

The government of Portugal expressed strong dissatisfaction over the "unilateral decision," accusing Washington of failing to take into account reservations conveyed in discussions in recent years.

Lisbon was "particularly concerned about the consequences of this decision on the economic and social situation on the island of Terceira," while the regional government of the Azores called it an "enormous slap in the face to the Portugese state."

Some of the forces withdrawn from Britain and elsewhere will be shifted to Germany and Italy, US officials said.

-- F-35 jets head to Britain --

The closure of Mildenhall, home to refueling tanker aircraft and special operations forces, will be offset in part by plans to station two squadrons of the new F-35 fighter jet at RAF Lakenheath within the next several years. The special operations unit at Mildenhall will be redeployed to Germany.

The moves will mean a net decrease of about 2,000 US military and civilian personnel in Britain, while in Germany, the 40,000-strong US force there will increase by several hundred troops over the next several years.

Britain played down the effect of the US decision to pull out of Mildenhall and instead focused on the plan to deploy F-35 squadrons to the country.

"Our historic relationship with the US remains as strong as ever, and their decision to base their first European F-35 squadrons in the UK clearly reflects the closeness of our partnership, as well as the American commitment to NATO and Europe," British Defence Secretary Michael Fallon said in a statement.

The move to end US operations at Mildenhall is "disappointing," Fallon said. "However, we recognize that such changes are sometimes necessary."

Despite the closures the United States remains committed to Europe's security, amid concern over Moscow's intervention in Ukraine.

"In the end, this transformation of our infrastructure will help maximize our military capabilities in Europe and help strengthen our important European partnerships so that we can best support our NATO allies and partners in the region," Pentagon chief Chuck Hagel said in a statement.

The Pentagon made a pointed reference to Ukraine, saying funds already approved by Congress will allow Washington to keep up joint exercises with eastern partners, pre-position additional hardware in Eastern Europe and "build the capacity of our newer allies as well as Ukraine, Georgia and Moldova."

The location of many US bases in Europe dates back to the aftermath of World War II and the tense years of the Cold War, and officials said new conditions and technology rendered some facilities obsolete.

The plan calls for pulling out from two smaller British air bases as well, RAF Alconbury and RAF Molesworth, where about 750 troops are stationed.

A number of barracks, commissaries and other facilities in Germany will be closed, and a few sites in Belgium and the Netherlands also will be shut down.

In Portugal, two-thirds of the military and civilian personnel at Lajes Field will be withdrawn and operations scaled back.