There is a risk that widespread disruption could ensue at a time when government and businesses continue to deal with the effects of COVID-19.
One of the most challenging areas will be Northern Ireland which will require some goods arriving from the rest of the UK to be checked in order to protect trade with EU member, Ireland.
"It has to be a fair agreement for both sides - we are not going to sign an agreement at any cost," Sefcovic told reporters after a meeting with Britain's Brexit supremo Michael Gove in London.
Britain left the EU in January and the estranged allies have since been locked in complex negotiations to try to agree a free trade deal for when a status-quo transition period ends on Dec. 31.
The European Union on Thursday said Britain needed to compromise to secure an agreement.
"But we have to bear in mind the realities because an agreement has to be in the interests of both sides, in the British interest and in the interest of the EU's 27 member states."
The current British position "creates a very difficult negotiation and a landing zone that is quite hard to envisage, quite frankly, for now", Coveney told a parliamentary committee.
This week's round of negotiations between the EU and London on a new trade agreement after Brexit, the last scheduled, failed to resolve all the outstanding issues, the sources said.
After Dec. 31, when a transition deal ahead of a full-blown Brexit ends, financial services companies in Britain will have to access the EU via its "equivalence" system.
The EU has already granted temporary access to UK clearing houses from January under this regulatory regime.
"We recognise that global supply chains are under significant pressure, exacerbated by recent events with COVID-19," the ministry's chief commercial officer, Steve Oldfield, wrote.
"Negotiating rounds will take place in August and in September, unless agreed otherwise between the parties," according to a document Frost posted on Twitter.
A long-awaited report by parliament's Intelligence and Security Committee (ISC) had been expected to shed light on possible Kremlin interference in the landmark vote that saw Britain leave the European Union.
London and Brussels are racing to agree a new trade deal for when Britain leaves the EU's single market and customs union on December 31, but talks have stalled.