LONDON - Prime Minister Theresa May's office insisted on Friday it would not "trap" Britain in an endless customs union with the EU after Brexit, amid reports some ministers could quit if this is the price of a divorce deal.
But her spokeswoman declined to confirm that a fall-back plan to keep open the land border with Ireland after Britain leaves the bloc in March 2019 would be "time-limited".
Negotiations in Brussels have stepped up ahead of a high-stakes EU summit next week, and May briefed selected members of her cabinet late Thursday on how she intends to get an agreement.
Several eurosceptic ministers are now reportedly considering resigning over plans to give ground on the so-called backstop arrangement.
Britain has proposed a customs arrangement with the EU to avoid physical checks between Northern Ireland and EU member Ireland, until the issue can be resolved with a wider trade deal.
A Downing Street spokeswoman emphasised on Friday that this would be "temporary", saying: "The prime minister would never agree to a deal which could trap the UK in a backstop permanently."
She repeated that Britain wanted a new trade deal by the end of December 2021 at the latest.
However, she declined to say the backstop would be "time-limited", a phrase which was in the original proposal published by London in June.
Brussels has insisted the backstop cannot by its very nature be time-limited.
However, British eurosceptics are wary of being tied to the bloc indefinitely.