LONDON (Reuters) – Britain needs a transition period to soften its exit from the European Union, but it cannot be used to stop Brexit, two senior ministers said on Saturday.

“We believe a time-limited interim period will be important to further our national interest and give business greater certainty – but it cannot be indefinite; it cannot be a back door to staying in the EU,” Chancellor of the Exchequer Philip Hammond and trade minister Liam Fox wrote in a joint article for the Sunday Telegraph newspaper.

Fox is one of the government’s most pro-Brexit ministers, and Hammond an outspoken pro-European, so that the joint letter represents an important agreement between two opposing factions within Prime Minister Theresa May’s cabinet.