LONDON (Reuters) - British and EU trade talks are at a “very difficult point”, a spokesman for Prime Minister Boris Johnson said on Friday, underlining that time was running out and that any agreement must respect British sovereignty. Talks in London went on until 11 p.m. on Thursday after they stumbled when the British side accused the European Union of bringing new demands to the talks, a charge denied by the bloc who described the charge as spin to extract more concessions. The negotiating teams have for weeks been unable to narrow the gaps on the thorniest issues, including fisheries and fair competition guarantees, and the spokesman said any further talks over the weekend were “contingent” on what happened on Friday. “We are committed to working hard to try to reach agreement with the EU. Talks are ongoing. There are still some issues to overcome. Time is in very short supply and we’re at a very difficult point in the talks,” the spokesman told reporters. “What is certain is that we will not be able to agree a deal that does not respect our fundamental principles on sovereignty and taking back control.” Some EU officials have said they expect a deal to come over the weekend, but when asked whether the talks would continue on Saturday and Sunday, the spokesman said: “These are live negotiations so I can’t give you an update on what’s happening over the weekend because this is contingent on the progress of the talks today.” Reporting by Elizabeth Piper and William James; editing by Michael Holden and Alistair Smout