Argentine President Nestor Kirchner has said Britain won a "colonial victory" in the Falklands War that was unacceptable in the eyes of the world.
The islands will return by "peaceful means", says Mr Kirchner
Mr Kirchner was speaking on the 25th anniversary of the end of the conflict over the islands in the south Atlantic, that Argentina calls the Malvinas.
Britain retook the islands on 14 June 1982, two and half months after the UK territory was invaded by Argentina.
Mr Kirchner vowed the islands would return by "peaceful means".
Some 255 British servicemen, more than 650 Argentines and three islanders were killed during the war.
"The Malvinas are Argentine and they will return to Argentina by peaceful means," President Kirchner said in Buenos Aires.
He said that Britain "may have won the battle because it's a world power but they will never win by reason or justice".
Unlike in Britain, no major commemorations were held in Argentina on 14 June.
The ceremonies in the UK centred at the Falkland Islands Memorial Chapel in Pangbourne, near London.
War veterans were joined by the Queen, Prime Minister Tony Blair and Baroness Thatcher, who as the then prime minister dispatched a British naval task force to the Falklands.