LONDON (AP) — British Prime Minister Theresa May faced resistance and potential rebellion from hard-core Brexit backers in her Conservative government Friday as she gathered her fractious Cabinet to hammer out a plan for future trade with the European Union.

Almost 30 Cabinet ministers were being sequestered inside the prime minister’s Chequers country retreat — without their phones — for all-day talks on a compromise plan that May hopes will unite the government, and be accepted by the bloc.

It’s a tall order.

With just nine months to go until the U.K. leaves the bloc, May said the government has “a great opportunity — and a duty” to agree upon a plan. But pro-Brexit ministers including Foreign Secretary Boris Johnson have doubts about her proposal, which would see Britain stick closely to EU rules for trade in goods.

Brexit-backing ministers believe that would limit Britain’s ability to strike new trade deals with the United States and other countries around the world. A more pro-EU group that includes Treasury chief Philip Hammond thinks it’s essential to retain close economic ties with the bloc and its market of 500 million people.

That view has been echoed by big manufacturers including Airbus and Jaguar Land Rover, who warn they could abandon Britain if the EU and the U.K. cannot strike a strong free trade deal. Airbus alone employs some 14,000 workers in Britain.

Airbus chief executive Tom Enders slammed the British government Friday, saying “Her Majesty’s government still has no clue, or at least no consensus, on how to execute Brexit without severe harm.”

Leading Cabinet Brexiteers including Johnson and Brexit Secretary David Davis met in private Thursday, sparking rumors some could quit if May does not alter her 120-page proposal.

But Cabinet Office Minister David Lidington, May’s second-in-command, was optimistic that a consensus would be reached in Friday’s talks, expected to last for 12 hours at the 16th-century manor house 40 miles (65 kilometers) northwest of London.

“I think at the end of the day we’ll get to an agreement and we’ll have an offer to put to our European colleagues,” he said.

As the British government bickers, EU leaders have grown impatient, warning May that she must present concrete and “realistic” proposals within weeks if there is to be a deal by the time the U.K. leaves on March 29, 2019.

The bloc has repeatedly warned Britain that it cannot “cherry pick” the benefits of EU membership, such as access to the customs union and single market, without accepting the responsibilities, which included allowing free movement of EU citizens to the U.K.

It is also demanding certainty on the future of the border between Britain’s Northern Ireland and the Republic of Ireland — the U.K.’s only land frontier with an EU member. Britain has promised to maintain an invisible border, free of customs posts and other infrastructure, but have not said how that can be achieved, given May’s insistence that Britain will leave the EU’s customs union.

The proposal May is presenting Friday — dubbed a “facilitated customs arrangement” — calls for the U.K. to use technology at its borders to determine whether goods are bound for Britain or the EU, and charge the appropriate tariffs. It would also commit Britain to keeping its regulations closely aligned to those of the EU for trade in goods and agricultural productions — but not in services, which accounts for the bulk of Britain’s economy.