Britain says it could refuse to pay the so-called Brexit 'divorce bill' to Brussels of there is no trade deal.
Brexit Secretary Dominic Raab, who replaced David Davis after he quit the role earlier this month, said "some conditionality between the two" was needed.
He added that the Article 50 mechanism used to trigger Britain's exit from the European Union provided for new deal details.
He told the Britain's Sunday Telegraph: "Article 50 requires, as we negotiate the withdrawal agreement, that there's a future framework for our new relationship going forward, so the two are linked.
"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.
"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."
"Inconceivable"
The British government has sent mixed signals so far on the bill.
UK Prime Minister Theresa May agreed in December to a financial settlement of €43bn that ministers said depended on agreeing future trade ties.
But her cabinet members have since cast doubt on the position.
The British Chancellor Philip Hammond said shortly afterwards that he found it "inconceivable" Britain would not pay its bill, which he described as "not a credible scenario".
The UK is set to leave the EU on March 30th next year, but the two sides want to strike a divorce agreement by late October in order to give the parliament enough time to endorse a deal.
Mr Raab said critics were mistaken to think Mrs May would not walk away without a deal if she had to.
"They're wrong. No bluffing," he told the Sunday Telegraph.
"The ball is now in the EU's court, and don't get me wrong, there will be plenty more negotiations, I've made that clear, but if they show us the same level of ambition, energy, pragmatism, this deal gets done in 12 weeks."
