Prime Minister Theresa May said on Friday the European Union would not renegotiate the Brexit deal if Britain's parliament rejected the current version of the exit agreement.
"I believe if we were to go back to the European Union and say 'well people didn't like that deal, can we have another one?' ... I don't think they're going to come to us and say we'll give you a better deal," she told BBC radio during a question and answer session with listeners.
Questioned repeatedly over whether she would resign if she loses a vote to approve the deal, expected in mid-December, she said her focus was on getting it through at the first attempt and not on her own future.
In a call-in show on BBC radio, May also refused to say whether or not she would resign if the British parliament eventually voted down the divorce agreement and outline on future ties.
"This isn't about me... I am focused on ensuring we get this deal," she said, adding that she would be touring Britain to explain the agreement "to people up and down the country".
"If this deal does not go through we are back at square one. What we end up with is more division and more uncertainty," she said.
May, who voted to stay in the European Union in the 2016 referendum, also dismissed calls for a second vote with an option to keep Britain in the EU, but then refused to say whether her deal was preferable to remaining in the bloc.
Instead, she said Britain could build a "better future" for itself outside the European Union.
She repeated her position on British sovereignty over Gibraltar -- a contentious issue with Spain that in recent days has threatened to upend the EU summit on Sunday.
"We're very clear, as the UK, that when we negotiate on these matters... we do so on behalf of the whole UK family including Gibraltar," she said.
May's spokeswoman told reporters earlier on Friday: "We've negotiated very openly and constructively with the EU in matters relating to Gibraltar and worked closely with Spain.
"The withdrawal agreement isn't being re-opened. We will work with the government of Gibraltar and Spain on our future relationship," she said.
May is due to travel to Brussels on Saturday for last-minute talks with European Commission President Jean-Claude Juncker ahead of the summit.
