Senior British ministers have agreed to offer more money to Brussels as part of Brexit negotiations, but only as part of a final deal on leaving the EU, sources said Tuesday.

Leading Brexit campaigners, including Foreign Secretary Boris Johnson, have agreed to increase Britain's offer of a financial settlement in a bid to move the withdrawal negotiations onto trade, newspaper reports said.

A government source confirmed to AFP that ministers at a cabinet sub-committee meeting late Monday had agreed to offer more money on the basis that it was part of a final deal, but said "no numbers" were discussed.

A Downing Street source said: "It remains our position that nothing's agreed until everything's agreed in negotiations with the EU. The UK and the EU should step forward together."

An unnamed source told the Daily Telegraph newspaper: "Any offer would be determinant on the overall progress of the negotiations, so it's not a case of 'take that money and bank on it'."