LONDON (Reuters) - Britain and the European Union are heading into a “very significant” week, British foreign minister Dominic Raab said on Sunday, as talks over a trade deal enter their final days with serious differences yet to be resolved. EU negotiator Michel Barnier told reporters in London that “works continue, even on Sunday” on his way to a negotiating session, as both sides look for a deal to prevent disruption to almost $1 trillion of trade at the end of December. “This is a very significant week, the last real major week, subject to any further postponement... we’re down to really two basic issues,” Raab told the BBC. Despite missing several self-imposed deadlines, the negotiations have failed to bridge differences on competition policy and the distribution of fishing rights. But Britain’s transitional EU exit agreement - during which the bloc’s rules continue to apply - expires on Dec. 31, and Britain says it will not seek any extension. A deal would have to be ratified by both sides, leaving little time for new delay. “The bottom line is... in the ordinary course of things we need to get a deal done over the next week or maybe another couple of days beyond that,” Raab told Times Radio in a separate interview. Earlier, he had signalled some progress on the ‘level playing field’ provisions which look to ensure fair competition between Britain and the EU, and said fishing remained the most difficult issue to solve. Despite accounting for 0.1% of the British economy, fishing rights have become a totemic issue for both sides. Britain has so far rejected EU proposals and remains adamant that as an independent nation it must have full control of its waters. “The EU have just got to recognise the point of principle here,” Raab told Times Radio.