Arriving for a special summit in Brussels on Sunday to vote on May's almost 600-page Withdrawal Agreement, which spells out the terms for Britain's exit on March 29, European Commission President Jean-Claude Juncker said it was a "sad day".
EU President Donald Tusk announced in a tweet that leaders of 27 remaining EU member states "endorsed" the plans to break off from the EU.
At their joint presser concluding a quick Sunday summit of all European Union leaders to approve the Brexit deal negotiated over 18 months, they refused to speculate on what would happen if British Prime Minister Theresa May loses the parliamentary vote.
May is struggling even to unite her ruling Conservatives, and Northern Irish parliamentary allies the Democratic Unionist Party, behind the plan.
"Spain is the physical and geographical gateway to Europe for Gibraltar", Picardo told the BBC.
Both sides have been making preparations for such a "no deal" scenario, though the European Union insists Britain has more to lose.
In the lead-up to a historic summit Sunday in Brussels, where a Brexit deal is expected to be rubber-stamped, tiny Gibraltar suddenly loomed large.
It also includes details on the length of Britain's transition period, whereby no major changes will be made to the UK-EU relationship, as the two parties work out a post-Brexit trade deal.
Spain threatened to derail the Brexit deal over concerns about its role in future trade arrangements involving Gibraltar - a British Overseas Territory with 30,000 residents.
"I am totally convinced this is the only deal possible".
"I believe that the British government will succeed in securing the backing of the British parliament", Juncker said, declining to comment on what might happen if May fails.
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On Friday wet weather was making it hard to reach the site, and among those that did few were in favour of women being allowed. Despite the police efforts, Desai was not allowed to leave the airport, forcing her to return to Mumbai late night yesterday.
Liberal Democrat Brexit spokesman Tom Brake claimed the PM had "caved in" and "appears to have cast the people of Gibraltar aside".
European Commission President Jean-Claude Juncker said anyone hoping for fresh negotiations would be disappointed within "seconds" if Parliament rejects the deal, while Austrian Chancellor Sebastian Kurz added: "This is a take-it-or-leave-it situation". She has left the status of Gibraltar in jeopardy.
"We have taken a decisive step towards resolving a conflict that has lasted more than 300 years between the United Kingdom and Spain", said Sanchez, calling Gibraltar a territory that is yet to be decolonized.
"So I will take this deal back to the House of Commons confident we have achieved the best deal available and full of optimism about the future of our country".
"If there was anything better I can tell you Theresa May would have gotten that", Dutch Prime Minister Mark Rutte told reporters.
"If [Parliament] did decide to back this deal we would have to decide to review the confidence and supply agreement", she said.
The Brexit package, which is very much the British Prime Minister Theresa May's deal, has been painstakingly crafted. "The British people don't want to spend any more time arguing about Brexit", she said.
Negotiations continued up to the last minute on the 585-page withdrawal agreement, which has drawn fierce criticism from euroskeptics as well as pro-EU politicians in Britain.
British and European Union negotiators will still have to work out the terms of their future relationship, and although a 36-page declaration also approved Sunday set out some of the guidelines, much remained unresolved, including Britain's freedom to control large parts of its own economy.
What's to follow if a vote in British Parliament doesn't set the Brexit plan in motion is still unclear.
Tusk, who represents EU leaders on the world stage, said he recommended "that we approve on Sunday the outcome of the Brexit negotiations" in a letter to members of the European Council.