Philip Hammond has dismissed suggestions that Brexit could be postponed or delayed, amid ongoing Tory tensions.
The Chancellor answered "No" and repeated the words of EU chief negotiator Michel Barnier that the "clock is ticking", before reiterating March 29 remains the date when Britain will leave.
He added the UK hopes talks on a post-Brexit EU trade deal will begin this autumn, delivering a less than certain verdict compared to an earlier upbeat Government assessment from Brexit Secretary David Davis's department.
Reports last week suggested Mr Barnier believes the next phase of negotiations would be delayed by two months to December because of disagreements over how much the UK owes the bloc.
This prompted the Department for Exiting the EU to state UK Government officials were "confident" sufficient progress will have been made by October to advance talks to the next stage.
Mr Hammond's remarks came during a press conference in Brazil, where he is leading a UK trade delegation.
He will also travel to Argentina while Alun Cairns is among the other members of Theresa May's ministerial team seeking to boost trade links ahead of Brexit, with the Welsh Secretary visiting Japan.
But at home Downing Street insisted free movement from the EU will end in March 2019 as Mrs May sought to contain a Cabinet row in which Mr Hammond and Home Secretary Amber Rudd have offered differing views to International Trade Secretary Liam Fox.
Mr Hammond, speaking after a meeting with Brazilian finance minister Henrique Meirelles, said of the UK's post-Brexit trade links: "We will be seeking to strengthen and deepen our ties with trading partners around the world - including Brazil."
Responding to questions, Mr Hammond also said: "No, it won't be postponed or delayed.
"As Michel Barnier, the EU negotiator says ... the clock is ticking, we are already in a timescale that has to end on March 29 2019, which is when Britain will leave the European Union.
"There's a discussion going on about how we then move from full membership of the European Union to a future relationship with the European Union and that's a debate, a discussion that will go on through this negotiations.
"What role can trade with Brazil play in Britain's transition to a new role in the world? A very important role.
"We will look to increase our trade relationships and our investment with traditional partners around the world.
"Britain has always been an outward-looking country and we have many strong and historic partnerships like the one with Brazil, and we will seek to build up our trade in both directions with those partners over the coming years as we leave the European Union and once again have the ability to conclude bilateral trade deals with friends and allies around the world."
Mr Hammond also reiterated that the UK's legal obligations with the EU will end on March 29 2019, including the jurisdiction of the European Court of Justice.
He went on: "Of course it is then possible for us as a sovereign nation to negotiate future relations with the European Union, and that's the process that we hope to begin this autumn - of discussion with our European Union partners about the future trading relationship with them.
"But that trading relationship will not be based on membership of the European Union, it will be based on treaty - just like a future trading relationship with Brazil will be based on treaty."