The country's biggest business lobby group, the CBI, said yesterday it wanted a deal by December to assuage fears of a radical change in the trading relationship with the EU after Britain leaves in March 2019.
Prime Minister Theresa May told MPs yesterday that arrangements for an implementation period could only come as part of a final deal on Britain's future relationship with the EU.
She accepted such a deal was not likely to be reached until the second half of next year -- although EU chief negotiator Michel Barnier warned that it could take "several years".
"But what we would also say in terms of the broad outline of an implementation period, we believe that we can agree that quickly."
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Finance Minister Philip Hammond added in the House of Commons: "We want to agree the principles of that period as soon as possible."
European leaders have yet to approve the formal start of talks on post-Brexit trade with Britain, saying there has not yet been enough progress on the divorce issues of money, Ireland and EU citizens' rights.
"Together with the broad support for the idea in parliament, this (decision by the EU) should give British businesses confidence that we are going to provide them with the certainty they require," Hammond said.
Barnier has said that any Brexit deal must be wrapped up by October 2018 to leave time for its ratification by the EU Parliament -- and Britain still insists a trade deal is possible by then.
"It will give us a little more time to prepare the future relationship," he said -- adding that the latter negotiation would take "several years".