Spain will seek to take its dispute with the UK over Gibraltar to the UN with the support of Argentina, according to Spanish media.
Spanish foreign minister Jose Garcia-Margallo is expected to propose that both countries present a “united front” over Gibraltar and the Falkland Islands, El Pais reported.
Mr Garcia-Margallo will sound out his Argentinian counterpart, Hector Timerman, during a meeting in Buenos Aires next month as he prepares for a “180 degree turn in policy towards the colony”, the newspaper said.
Such a move would be seen as an escalation in the diplomatic tensions surrounding the overseas territory.
Argentina is on a two-year term as non-permanent member of the UN’s Security Council and could use its position to include discussions over Gibraltar on the agenda.
The country’s president, Cristina Kirchner, used a meeting of the council this week to renew demands for talks over the sovereignty of the Falklands.
Spain is also considering the possibility of raising the matter of Gibraltar at the UN’s General Assembly or the International Court of Justice at The Hague, diplomatic sources reportedly told El Pais.
A Foreign Office spokeswoman said: “Our policy on Gibraltar has not changed and is consistent with our policy on other overseas territories. Self-determination matters more than territorial integrity.
“The people of Gibraltar have repeatedly and overwhelmingly expressed their wish to remain under British sovereignty.”
Political tensions flared after the British territory began work on a concrete reef in the Mediterranean which Spain claims will destroy fishing in the area.