The UK still believes it can agree a post-Brexit trade deal with the EU next month, according to Downing Street.
The PM’s spokesman said UK negotiators would “continue to plug the gaps” when talks enter their seventh round in Brussels on Wednesday.
The two sides remain divided over competition rules, fishing rights and how a deal would be enforced.
The UK has ruled out extending the December deadline to reach an agreement.
This week’s talks are the last scheduled negotiating round ahead of the autumn, although both sides have previously said talks would continue in September.
EU chief negotiator Michel Barnier had dinner with UK counterpart David Frost on Tuesday evening, with talks set to conclude on Friday.