Downing Street has said the sovereignty of the Falkland Islands "rests with the UK", following a report the US could review its position on the British claim to the territory.
The internal Pentagon email, which was first reported by Reuters, suggested the US was considering options to punish Nato allies it believed failed to support its war on Iran.
The options discussed also included seeking to suspend Spain from Nato over its opposition to the war.
Asked about the report, a No 10 spokesman said: "The Falkland Islands have hugely voted overwhelmingly in favour of remaining a UK overseas territory, and we've always stood behind the islanders' right to self-determination and the fact that sovereignty rests with the UK."
BBC News has not seen the Pentagon email.
