The UK's Brexit Secretary Dominic Raab says a deal will be done by October.
He told the BBC's Andrew Marr Show that 80% of the UK-EU withdrawal agreement is already settled.
Earlier, he told The Sunday Telegraph paying the divorce bill would depend on the EU "fulfilling its side of the bargain".
He also claimed Britain could refuse to pay its divorce bill to Brussels if it does not get a trade deal.
"You can't have one side fulfilling its side of the bargain and the other side not, or going slow, or failing to commit on its side.
The UK's Brexit Secretary Dominic Raab at the EU Commission headquarters in Brussels | Image: Monasse Thierry/ANDBZ/ABACA/ABACA/PA Images
"So, I think we do need to make sure that there's some conditionality between the two."
He added: "Certainly it needs to go into the arrangements we have at international level with our EU partners.
"We need to make it clear that the two are linked."
But he's confident a deal can be brokered through ongoing negotiations.
"80% of the withdrawal agreement (is) settled now, so that's good progress.
"I'm going back out on Thursday because on the future relationship in our White Paper - we've got a principled, ambitious, pragmatic plan.
"They've got questions on it... but actually if it's reciprocated, the energy we're going to bring to these negotiations, the ambition and the pragmatism - we get a deal done in October".
