Sefcovic spoke in the European Parliament during a plenary session that followed the European Council meeting held at the end of the previous week. The European Commission vice-president said that he understood the concerns raised by lawmakers over the UK's failure to implement the Withdrawal Agreement in full and over London's attempts to revise the agreement.
Several lawmakers "made it very clear that there cannot be a new deal unless the last one is properly respected," Sefcovic stated, adding that he thought this matter was "very clear, very simple."
Negotiators from both London and Brussels have just over two months to conclude a comprehensive agreement to avoid trading on World Trade Organization terms from 1 January onwards. Sefcovic told the parliament that his recent conversations with Michael Gove, a UK cabinet minister, had been encouraging.
"At the same time, I have to say that this Monday I was encouraged, because we had a good, constructive discussion with Chancellor Gove. I think we are advancing very well on guaranteeing citizens' rights as we promised to UK and EU citizens in the Withdrawal Agreement," the European Commission vice-president said.
The UK's controversial Internal Market Bill, which looks to revise earlier commitments on state aid and customs regulations in Northern Ireland that were included in the Withdrawal Agreement, has drawn the ire of the European Union.
Brussels has accused UK Prime Minister Boris Johnson's government of attempting to violate international law by revising the prior agreement.