Britain's chief negotiator David Frost said on Friday the government was concerned that time was running out for a post-Brexit trade deal with the European Union before a mid-October deadline.
Frost said "outlines of an agreement are visible" in many areas but there was "limited progress" on fair competition and state subsidy rules, and a deal on fisheries looked "impossible" without EU movement.
"I am concerned that there is very little time now to resolve these issues ahead of the European Council (EU summit) on 15 October," he added after a week of talks with EU counterpart Michel Barnier.
For his part, Barnier said "persistent, serious divergences" remained in the talks, which are aimed at securing a new trading relationship once Britain leaves a post-Brexit transition period at the end of this year.
Frost said that overall his meetings with Barnier this week "were constructive discussions conducted in a good spirit".
"For our part, we continue to be fully committed to working hard to find solutions, if they are there to be found," the British diplomat said.
A possible deal was in sight on areas such as trade in goods and services, transport and energy, he said. But the stumbling blocks of state aid and fisheries were "fundamental to our future status as an independent country".
There had been "some limited progress" on state subsidies. But on fishing rights, "the gap between us is unfortunately very large and, without further realism and flexibility from the EU, risks being impossible to bridge".
Britain left the EU in January after nearly 50 years of integration but remains bound by the bloc's rules until December 31 while both sides thrash out the terns of their new relationship.
Prime Minister Boris Johnson has repeatedly refused to extend the so-called transition period, despite the tight timetable for talks and disruption caused by the coronavirus outbreak.
Failure to strike a deal would see Britain and Europe revert to World Trade Organization terms, with higher tariffs and quotas.
