Argentina and Spain agreed Thursday to work together to persuade Britain to negotiate the future of the Falkland Islands and Gibraltar, Argentina said.

Both territories -- the Falklands in the South Atlantic, which Argentina calls the Islas Malvinas, and Gibraltar at Spain's southern tip -- are controlled by Britain.

EU inspectors assessed customs controls at Gibraltar's border with Spain on Wednesday, aiming to soothe a feud between London and Madrid over the territory.

Workers who habitually cross the border complained that the visit should have been unannounced to avoid window-dressing by the Spanish border guards they blame for long queues at the crossing.

An EU team tasked to defuse a bitter feud between Spain and Britain over Gibraltar will center on tit-for-tat allegations of smuggling and border control abuses, the European Commission said Tuesday.

The team, which begins work on Wednesday, will attempt to soothe the row dividing London and Madrid over the British Mediterranean outcrop.

Prime Minister David Cameron pledged Britain would "always stand up for Gibraltar" as he met the British territory's chief minister on Friday for talks on its border spat with Spain.

Cameron welcomed Fabian Picardo for talks at his Downing Street office in London, as Spain's deputy prime minister in Madrid stressed the need for dialogue on cross-border issues.

Russia "over the next few days" will be sending an anti-submarine ship and a missile cruiser to the Mediterranean as the West prepares for possible strikes against Syria, the Interfax news agency said on Thursday.

"The well-known situation shaping up in the eastern Mediterranean called for certain corrections to the make-up of the naval forces," a source in the Russian General Staff told Interfax.

Spain told Britain on Tuesday it must remove 70 concrete blocks dropped into the waters off Gibraltar before Madrid will agree to dialogue in a heated dispute over the British outpost.

In an article in the Wall Street Journal, Foreign Minister Jose Manuel Garcia-Margallo sharply criticized Gibraltar's creation of the reef last month in disputed waters that were used by Spanish fishermen.

The European Commission said Monday that imposing taxes or toll fees at EU member-state borders would be "illegal", as a diplomatic tug-of-war between Britain and Spain over Gibraltar escalated.

"We can confirm that any tax (or) fees imposed at the border of a member state will be illegal under EU law," Commission spokesman Olivier Bailly told a news briefing in Brussels.

British frigate HMS Westminster docked in Gibraltar on Monday in a naval exercise coinciding with a furious diplomatic row with Spain over sovereignty and fishing rights in the surrounding waters.

The frigate, equipped with a Type 23 weapons system including a magazine torpedo launcher, Harpoon anti-ship missiles, Sea Wolf surface-to-air missiles and helicopter, arrived at the British outpost in the morning.

Situated in sight of unstable north Africa and on the shipping route to the Middle East, Gibraltar has military and intelligence facilities that still make it a strategic asset for Britain, analysts say.

Spain ceded Gibraltar to Britain in perpetuity in 1713 following a military struggle but has since the 1960s fought to have the territory returned to Spanish sovereignty.

British Prime Minister David Cameron has called on European Commission president Jose Manuel Barroso to send monitors to observe "politically motivated" checks at Spain's border with Gibraltar as soon as possible, Downing Street said Friday.

A row has broken out between London and Madrid over Gibraltar, after Spain introduced stringent border checks which have led to waits of up to five hours for motorists trying to enter the British-held territory.