Spanish Prime Minister Pedro Sanchez has warned that he may vote against the Brexit agreement between the European Union and the United Kingdom because the negotiations regarding Gibraltar "remain distant".
The EU and the UK reached an interim agreement on Thursday on the relationship they hope to build after Brexit, but the 26-page political declaration does not contain a single mention of Gibraltar.
Located to the south of the Iberian Peninsula, Gibraltar is a disputed British overseas territory. Spanning just 6.8 square kilometres and with around 30,000 inhabitants, it has become the main obstacle in getting EU approval on the draft deal.
Spain has asked for changes to the UK's withdrawal treaty and the accompanying political declaration to make clear that any decisions about Gibraltar would only be taken with Madrid.
But why is Gibraltar so important to Spain?
Euronews spoke to Miguel Ángel Benedicto Solsona, a professor of international relations at the European University, to find out what issues in Gibraltar Spain wants a say in.
Solsona told Euronews that Spain wants to solve issues related to Gibralter serving as a tax haven.
Thousands of companies have been established on the overseas territory, many of which carry out their activity on the other side of the Spanish border, he explained.
Rights of Spanish workers
There are more than 10,000 workers who cross the border from the Campo de Gibraltar to work on Gibraltar each day, Solsona said.
The Campo de Gibraltar area has one of the highest unemployment rates in Spain.
After Brexit "let's see what happens with the rights of these workers ... who will pay their pensions, what will happen to them?" Solsona asked.
The Strait of Gibraltar is a short distance from Morocco, and since the 1990s, tobacco smuggling there has increased dramatically.
According to figures from Diario de Cádiz, 26% of Gibraltar's budget "comes from the importation of 72 million packs [of tobacco] per year", which is equivalent to €180 million.
"There is a lot of illegal smuggling of tobacco between Gibraltar and Spain and Spain is interested in this ending somehow,” Solsona explained.
Another problem Spain has an interest in is the environment.
"The polluting spill that Gibraltar sometimes sends to the Mediterranean... harms the Spanish Mediterranean coast."
Spain would also like a deal to include the joint management of Gibraltar's airport.
However, Solsona said it would be difficult for the British government to give any authority to police or the Spanish Civil Guard in supervising passengers in this transit zone.
The best solution?
Solsona said he hopes that Spain and the UK will agree on a special protocol for Gibraltar, taking inspiration from the border with Northern Ireland or the British bases in Cyprus.