Argentine President Cristina Fernandez de Kirchner says Latin American leaders have backed its objections to oil exploration in the British-controlled Falkland Islands.
Argentina has claimed the South Atlantic islands, known as the Malvinas in Spanish, since Britain established rule in the 19th century.
It invaded them in 1982, but after a two-month war was forced to withdraw.
However, it still claims the archipelago and says oil exploration by Britain's Desire Petroleum is a breach of sovereignty.
'There continues to be systematic violation of international law that should be respected by all countries,' Ms Fernandez de Kirchner told the opening session of a regional summit near the Mexican resort town of Playa del Carmen.
'In the name of our government and in the name of my people I am grateful ... for the support this meeting has given to our demands,' Ms Fernandez de Kirchner said.
Mexican President Felipe Calderon said the group had approved a document supporting Argentina in the territorial dispute.
Venezuelan Hugo Chavez addressed Queen Elizabeth directly on his weekly television programme, telling her to return the Falklands to Argentina. He repeated his demand late on Sunday when he arrived in Mexico for the summit.
'We support unconditionally the Argentine government and the Argentine people in their complaints,' Mr Chavez told reporters at the airport. 'That sea and that land belongs to Argentina and to Latin America.'
Escalating the dispute, Argentina formally objected to British-led drilling plans near the islands, and said it would require all ships from the Falklands to obtain permits to dock in Argentina.
Ms Fernandez de Kirchner said Argentina would not consider more serious measures like shipping blockades.
'Argentina will not take any step that is not framed in international law,' she told reporters.
While the Falklands are not an oil producer and have no proven reserves, oil companies are betting offshore fields may hold billions of recoverable barrels of oil.
Desire Petroleum said it broke ground at a well on its offshore 'Liz' prospect, which could contain up to 400m barrels, although there is a possibility the exploration will recover nothing.
British Defence Minister Bill Rammell said the government will take 'whatever steps are necessary' to protect the islands, which had a 'legitimate right' to develop an oil industry within its waters.