MADRID • Spain and Britain reached a preliminary agreement to keep the Gibraltar land border open, just hours before Britain's full exit from the European Union.

As part of Thursday's agreement, Gibraltar, a British Overseas Territory located on Spain's southern tip, will remain part of EU agreements such as the Schengen Area, Spanish Foreign Minister Arancha Gonzalez Laya said.

All the details of the agreement will be settled between Spain and Britain during a six-month transition regarding the territory, she said. "Spain, as member state representing the Union, will be responsible for enforcing Schengen and will be assisted by (EU border agency) Frontex for around four years, conducting controls both in Gibraltar's port and airport."

Gibraltar was not part of a last-minute deal last week for Britain's post-Brexit ties with the EU.

Without Thursday's agreement, tens of thousands of Spaniards and Gibraltarians who cross every day would have been forced to go through passport checks.

Spain still claims sovereignty over the port at the mouth of the Mediterranean which it ceded to Britain in 1713 after a war.

Ms Laya said the initial agreement safeguarded both countries' "un-renounceable aspirations of sovereignty".

Some 99 per cent of Gibraltarians rejected any idea of Britain sharing sovereignty with Spain in a 2002 referendum. Most of them voted to remain in the EU in Britain's 2016 Brexit referendum.

British Prime Minister Boris Johnson hailed the agreement in a tweet, saying: "I wholeheartedly welcome today's political agreement between the UK and Spain on Gibraltar's future relationship with the EU. The UK... will remain totally committed to the protection of the interests of Gibraltar and its British sovereignty."

The Schengen Area is a 26-country zone covering most of the EU, and a handful of non-EU members, where internal borders have been abolished.

REUTERS