Britain wants a transition after Brexit that will avoid businesses having to adjust to new rules and regulations twice.
It was believed that the details of how it would work in practice would be dealt with then.
"If these differences persist, a transition is not a given", Barnier said. "Time is short - very short - and we haven't a minute to lose if we want to succeed".
Japanese firms have spent billions of pounds in Britain over the past decades, encouraged to set up in the country by successive governments promising a business-friendly base from which to trade across the continent.
UK Prime Minister Theresa May had promised finance chiefs in January that an agreement on such a period would be reached by the end of next month.
The decision to make a showpiece address - which the Prime Minister had appeared to back away from - is revealed as No 10 confirmed an "away day" for warring cabinet ministers at Chequers. May's office did not respond to requests for comment.
"So it is as simple as that", Koji Tsuruoka told reporters.
"I hope we can resolve these issues with a broad trade agreement", he said.
According to senior British officials, under plans set out by Theresa May yesterday, Britain will diverge from a series of key European Union rules and regulations but keep the power to go back in at a later stage.
The UK has already committed to avoiding any kind of hard border between Northern Ireland and the Republic after Brexit. And I do not think it was in good faith to publish a document with frankly discourteous language, and actually implying that they could arbitrarily terminate in effect the implementation period. It has therefore to accept all the rules and the obligations until the end of the transition.
But on Friday, the EU's chief negotiator was clear that fudging the issue is not sustainable.
THERE were calls last night for a united push for special status for the north after Michel Barnier's warning that border checks will be "unavoidable" under UK plans to leave the single market and customs union.
The terms of the transition must also be addressed. And because of Japan's intertwined ties with Britain's economy, it is fast trying to position itself as a key influence over what the final Brexit deal will look like.
The plaintiffs in the case are five British expatriates living in the Netherlands and two private organizations-Brexpats and the Commercial Anglo Dutch Society [advocacy websites]-who claim that the expatriates have rights as European Union citizens that are independent of rights flowing from the citizenship in an European Union member state.
"The time has come to make choices".
"British businesses have heard enough talking - what's needed now is a concrete solution to enable all those involved in moving goods and services across the UK's borders to plan with certainty for a post-Brexit future", said James Hookham, the FTA's deputy CEO.