LONDON (Reuters) – Britain can only come up with a figure for a financial settlement with the European Union when a Brexit deal has been agreed, trade minister Liam Fox said on Sunday, warning leaders not to believe London is bluffing over a no deal.

Fox, speaking on ITV’s Peston on Sunday television program, said Britain would offer the other 27 EU members “further assurance” on its divorce before the next summit in December to push talks forward to a discussion of a future trading relationship.

“I don’t know what that number is but it’s very clear that we could only have that final number as part of a final agreement, we would want to know what the end state is,” Fox said.

“Away from the hyperbole around the divorce bill there is actually a great deal of cooperation going on between us.”

After Prime Minister Theresa May won a reprieve in the talks after a summit last week, the government will show the EU that “we are moving in the right direction” on the first phase of talks, which include the so-called divorce bill, he said.

But he also said the EU should not believe that Britain was bluffing by saying it was preparing for a no deal, describing trading according to World Trade Organization rules as “not exactly a nightmare scenario”.

“But I would prefer to have a deal,” he added.