"The financial and economic impact that this measure causes, both for Terceira Island and for the Azores archipelago has a very negative weight that the United States of America cannot but attend to," Pedro Passos Coelho said during a fortnightly debate in parliament.

The government "will be sure to raise this question" at a meeting of the permanent bilateral commission scheduled for next month "and, if it is necessary, to seek the revision of the technical accord," he said.

According to Passos Coelho, he has received from the US authorities signs of "openness... to try to find with Portugal responses that could mitigate this effect" of the winding down of the base.

"But obviously, so far, what we've had is a lot of word and little action," he said, adding that what is needed is "more practical consequences" of the vaunted readiness to act.

The US Defense Department last week announced that it would this year gradually reduce the Portuguese workforce at Lajes to 400 from the current 900, as it winds down the military presence there. The base is the largest single employer on the island.

The Azores regional government is next week to unveil a plan for the "economic revitalisation" of Terceira, which it says it has prepared "in secret" for two years in case the US took the decision just announced. However, it has said it requires funding to be implement.