Negotiators from the U.K. and EU reached a draft Brexit deal in 11th-hour talks Thursday, although there are serious doubts that the agreement will be approved by U.K. lawmakers back in Westminster. Sterling rose on news after the U.K. made concessions over the Irish border, an issue that had proven to be the biggest obstacle to a deal. The pound was 0.8% higher against the dollar, at $1.2929, reaching a five-month high but soon trimmed those gains as opposition parties in the U.K voiced their concerns. "We have a great new Brexit deal," U.K. Prime Minister Boris Johnson tweeted. He called on British lawmakers to back the deal when it's put before Parliament on Saturday. Tweet European Commission President Jean-Claude Juncker called the deal "fair and balanced." Tweet The "Withdrawal Agreement" was also approved by EU leaders at their summit on Thursday, but it still needs to pass U.K. lawmakers at the weekend. The EU Parliament will also have to ratify the deal at an as yet unspecified date. Speaking after the deal was announced, Michel Barnier, the EU's chief Brexit negotiator, said the deal was the result of intense work from both negotiating teams. "We have delivered together," he said.

Giving further details on the deal, Barnier said that Northern Ireland will remain part of the U.K.'s customs territory and would be the entry point into the EU's single market. He said there would be no regulatory or customs checks at the border between the Republic of Ireland and Northern Ireland (a part of the U.K.). That removed what had been a key issue for both sides. He added that Northern Ireland would remain aligned to some EU rules, notably related to goods. The deal also covers the protection of citizens' rights and a transition period that will last until the end of 2020. Barnier also said the EU and U.K. would work toward an "ambitious free trade deal with zero tariffs and quotas."

Deal already in doubt

Johnson faced a Saturday deadline by law to request an extension to the current Brexit departure date of Oct. 31 had no deal been reached. However, Juncker has implied that EU leaders won't allow an extension, even if Johnson asks. This sets up a complicated and difficult day for the U.K. Parliament on Saturday. There are doubts a deal will be approved in Westminster, with opposition parties already criticizing it. While details of the new deal remain scant, the U.K. opposition Labour party said in a statement that "from what we know, it seems the Prime Minister has negotiated an even worse deal than Theresa May's, which was overwhelmingly rejected." The pro-Remain Liberal Democrats also said they were determined to stop Brexit altogether and still advocated a second referendum. The leader of the Brexit Party, Nigel Farage, said the deal should not be supported. The Scottish National Party (SNP) has also said it will not vote for the deal. A key ally of the government, the Northern Irish Democratic Unionist Party (DUP), has already responded by saying that it cannot support the deal. The U.K. government, which does not have a majority in the British Parliament, needs the DUP's votes to approve the deal.

UK Prime Minister Boris Johnson and Jean-Claude Juncker, president of the European Commission, ahead of the opening sessions of the European Council summit at EU headquarters in Brussels. Stefan Rousseau | PA Images | Getty Images