Video report by ITV News Political Correspondent Romilly Weeks
Theresa May has said she is "confident" Britain can complete negotiating a free trade deal with the European Union before Brexit day.
The UK's withdrawal is expected by the end of March 2019.
During questioning at the Commons Liaison Committee, the prime minister said: "That is what we are working to and that is what I believe we can do."
She added: "The reason I'm confident that we can do this within the time concerned is because we start off from a different point.
"So we haven't got a situation where country A is coming to negotiate with the EU not having had any arrangements with the EU before."
The prime minister also acknowledged that any new trade agreement cannot be signed until after the UK leaves the bloc.
Mrs May's comments come after EU chief negotiator Michel Barnier said he wants an agreement on the future relationship finalised by October 2018.
Mr Barnier also insisted said the "logical end" of British transition period out of the EU must be at the end of 2020.
Mr Barnier also stressed that the UK would be expected to continue abiding by EU rules throughout the transition - including allowing the free movement of people within the bloc.
"This cannot be an a la carte transition period, the EU regulatory framework and all EU policies would still apply," he said.
Mrs May told the select committee she still sees a post-Brexit transition period lasting "around two years".
She added: "We will be quickly into negotiations into what the implementation should cover."
"We will obviously have to discuss because this is a practical issue about how long certain changes would need to be put in place."
Mrs May also rejected suggestions from SNP MP Angus MacNeil that she had been forced to "beg" for a transition period after losing several weeks' negotiating time to the snap general election.
"I haven't begged the European Union for two more years," said the prime minister said.
"This is not two more years to negotiate with the EU.
"This is two years when practically both businesses and governments will be able to put in place the changes necessary to move from the current relationship to the future partnership we will have."