Spain is warning of disruption for workers, tourists and businesses if no deal is agreed over Gibraltar's border before the UK's Brexit transition period with the EU ends.
Gibraltar, a British colony off the southern tip of Spain's mainland, was not included in the Brexit trade deal announced on Christmas Eve to reorganise the commercial and trade relations between the EU and UK.
The deadline for Gibraltar remains January 1, when a transitionary period regulating the border between Gibraltar and Spain expires.
Spain succeeded in convincing the EU to separate the issue of Gibraltar from the greater Brexit negotiations, meaning that Madrid is handling all talks directly with its counterparts in Gibraltar and London.
Spanish foreign minister Arancha Gonzalez Laya said if an agreement is not reached, she fears that the long lines of stranded lorry drivers seen at the English Channel crossing this past week could be repeated.
Ms Gonzalez Laya told Spanish state broadcaster RTVE: "We do not have much time, and the scenes of chaos from the UK must remind us that we need to keep working to reach a deal on Gibraltar. Spaniards want one, the people of Gibraltar want one, now the UK needs to desire one as well. Political will is needed."
Throughout the Brexit talks, Spain has insisted it wants a say on the future of Gibraltar.
The Rock was ceded to Britain in 1713, but Spain has never dropped its claim to sovereignty over it. For three centuries, the strategic outcrop of high terrain has given British navies command of the narrow seaway from the Mediterranean Sea to the Atlantic Ocean.
"Neither side is going to renounce its pretensions of sovereignty, but we must set that aside to reach a deal that makes lives easier for those living on both sides of the border," Ms Gonzalez Laya said.
More than 15,000 people live in Spain and work in Gibraltar, making up about 50% of Gibraltar's workforce. Gibraltar's population of about 34,000 was overwhelmingly against Britain leaving the European Union. In the UK's 2016 Brexit referendum, 96% of voters in Gibraltar supported remaining in the continental bloc that they feel gives them more leverage to deal with the government in Madrid.
The territory still remembers how, in 1969, Spanish dictator General Francisco Franco closed the border in an attempt to wreck Gibraltar's economy.
Gibraltar Chief Minister Fabian Picardo said the post-Brexit trade deal "is a huge relief given the potential difficulties that a no-deal Brexit might have created for the United Kingdom and the European Union".
But he added that his territory is still at risk.
Mr Picardo said: "This deal does not cover Gibraltar. For us, and for the people of the Campo de Gibraltar around us, the clock is still ticking.
"We continue to work, hand in glove with the United Kingdom, to finalise negotiation with Spain of agreement for a proposed treaty between the EU and the UK in relation to Gibraltar."
Mr Picardo recently told Spain's Cadena SER radio that "an agreement in the fashion of Schengen would be the most positive" outcome to facilitate the 30 million annual border crossings between Gibraltar and Spain.
Europe's Schengen area consists of nations who have agreed to eliminate general travel checks within the group, although some local checks have been reintroduced due to the coronavirus pandemic. The UK is not in the Schengen group.
The UK Government has said it is committed to finding a solution that includes "ensuring border fluidity, which is clearly in the best interests of the communities that live on both sides".