The progress made in post-Brexit trade talks between the UK and EU has been disappointing, Michel Barnier has said.
The EU’s chief negotiator said “genuine progress” and a decision on whether to extend the transition period were both needed by June.
Mr Barnier, who held talks with UK negotiator David Frost this week, warned that the “clock was ticking”.
The two sides will hold further rounds of talks before the end of the transition period in December.
Mr Barnier said a joint decision would be taken on 30 June about whether to extend the transition period.
But the UK government has already said it will refuse to extend it beyond December, even if the EU requested a delay.
At the Brussels press conference, Mr Barnier said: “The UK has affirmed once again this week its wish to make tangible progress between now and June and we’re on the same wavelength on this and we respect the same timetable.
“That means that we need genuine progress by June if, at the end of this year, we want to strike an agreement which is commensurate to the level of our economic interdependence and geographical proximity.”
But he said there were four areas where progress was “disappointing”, including the level playing field (what kind of access the UK could have to the European single market after Brexit), justice and fisheries.
Mr Barnier said the UK negotiating team keeps repeating that they are negotiating as “sovereign equals”, but the “reality” was that an agreement was being sought between a massive bloc and a smaller nation.
He said the two sides “need to find solutions on the most difficult topics”.
“The UK cannot refuse to extend transition and at the same time slow down discussions on important areas,” he said.
Mr Barnier reiterated that the UK would have to pay a “lump-sum” contribution to the EU budget if the transition period is extended beyond 31 December.
And he said any deal agreed by December would have to be “smart” to “cushion the blow” of Brexit and coronavirus.
The next round of talks are due to be held during the weeks beginning 11 May and 1 June.