Mercosur, a trading block that includes Uruguay, Paraguay, Brazil and Argentina, announced on Monday that it had banned boats with a Falkland Islands flag from its ports.

“We are very concerned by this latest Argentine attempt to isolate the Falklands Island people and damage their livelihoods, for which there is no justification,” a Foreign Office spokesperson has said.

“It’s not immediately clear what practical impact this statement will have… But no one should doubt our determination to protect the Falkland Islanders’s right to determine their own poltical future.”

A copy of the agreement circulated by the Argentine Foreign ministry says that all four countries involved vowed “to adopt… all the measures it is possible to impose to impede the entry of boats flying the illegal flag of the Malvinas Islands.”

This development in the relations between Argentina and Great Britain comes shortly after news that Argentine athletes announced plans to wear special kit at next summer’s London Olympics emblazoned with Falklands badges.