Brexit Secretary David Davis has signalled he is prepared to accept a shorter transition period than the UK wanted.
Davis said he could "live with" the proposed arrangement ending in December 2020, rather than the March 2021 date the UK has asked for if that would help secure a deal.
The Brexit Secretary, who is to meet the EU's chief negotiator, Michel Barnier, on Monday (March 19), said the EU and the UK would establish a joint committee during a transition period to guarantee a "duty of good faith" by both sides.
Theresa May has called for an implementation period of "around two years" after Britain formally quits the EU in March 2019.
Davis said his priority was to secure an agreement on the transition phase at next week's EU heads of government summit, telling BBC2's Newsnight: "That is more important to me than a few months either way. So, I'm not bothered too much about the question of whether it is Christmas 2020 or Easter 2021."
Asked if he could live with the transition ending in December 2020, Davis said: "I would live with that. We are still in the middle of a negotiation. Frankly, what I would not do is delay the decision in order to get a month or two more."
Davis downplayed concerns expressed by arch-Brexiteer Jacob Rees-Mogg that Britain would be a "vassal state" during the transition.
The Brexit Secretary said most EU laws take two years to pass, which is three months longer than the proposed transition timetable.
Davis said: "It is not going to be a big material issue. But we want to have in place, and we will have in place, is a joint committee which will oversee any issues like this that come up and a duty of good faith, good faith on both sides so neither side is disadvantaged. So, we won't fall into Mr Rees-Mogg's interesting definition of our position."