But British Prime Minister Theresa May said that London might still ask for a short extension of a planned transition period to ease its exit from the European Union.
Speaking to lawmakers about an EU leaders summit held last week, May said that there were limited circumstances in which an extension could be preferable.
She also told parliament that 95 percent of Britain's Brexit deal had been agreed but repeated her opposition to a European Union proposal for the Irish border, a major stumbling block, as criticism within her party grows.
"Mr. Speaker taking all of this together 95 percent of the withdrawal agreement and its protocols are now settled. There is one real sticking point left, but a considerable one," Ms May said.
"Which is, how we guarantee that in the unlikely event our future relationship is not in place by the end of the implementation period, there is no return to a hard border in Northern Ireland and Ireland."
With just over five months until Britain is scheduled to exit the EU, talks have stalled over a disagreement on the so-called Northern Irish "backstop", an insurance policy to ensure there will be no return to a hard border on the island of Ireland if a future trading relationship is not agreed in time.
May's attempts to unlock the Brexit negotiations by considering an extension to the transition period beyond an end date of December 2020 has angered pro- and anti-EU factions in her Conservative Party.
"The second step is to create an option to extend the implementation period as an alternative to the backstop. Mr. Speaker, I've not committed to extending the implementation period," ms May said.
"I do not want to extend the implementation period and I do not believe that extending it will be necessary."
"I see any extension, any extension or being in any form of backstop as undesirable. By far the best outcome for the UK, for Ireland and for the EU is that our future relationship is agreed and in place by the 1st of January 2021."
The extent of opposition to her plans could be laid bare on Wednesday when pro-Brexit lawmakers, including the Northern Irish party that props up her minority government, plan to stage a rebellion on a piece of legislation related to the province.