London: Brexit talks will resume with Prime Minister Theresa May under pressure on two fronts: European negotiators are pushing her to reveal her hand, while the opposition Labour Party has made a bid to lure May's critics to their side.

Labour's announcement on Sunday that it wants Britain to stay in the European Union's single market and customs union for up to four years after it leaves the bloc - a proposal that will delight business - means it's now worthwhile for Conservative parliamentarians who want to maintain ties with Europe to rebel and seek cross-party deals. May, who wants to leave the single market in 2019, lacks a parliamentary majority.

The move comes just as May's deeply divided cabinet had started to reach a consensus about what Brexit - and the first years after the split - should look like. As the next round of divorce talks gets underway on Monday, shifting domestic politics will once again hang over the negotiations.

"There is now a real chance that the UK could stay in a customs union forever," Charles Grant, director of the Centre for European Reform, said on Twitter. "But a few Tory rebels are needed."

While it's not clear whether European officials would welcome the Labour proposal, the party will soon have the chance to test support at home for its idea. Legislation that seeks to prepare Britain for leaving the EU returns next month to Parliament, and MPs are expected to battle over amendments.

"Labour has created an opportunity for Britain to avoid inflicting on itself the economic costs inherent in the government's chosen path," former Labour Business Secretary Peter Mandelson, usually a critic of his party's current leadership, wrote in the Financial Times.

"But achieving this depends on what others in Parliament do, including those on the Tory benches who know the risks of turning a crisis into an economic calamity. Labour has done Parliament and the public a big favour in starting what will be a complicated debate," he said.

May's government wants to leave the single market and customs union in March 2019, but then have a transition period of up to three years to allow both sides to adapt. Labour argues there isn't time to negotiate a transition deal as well as a final Brexit deal.

Many who oppose Brexit like the idea because it would also give voters more time to change their minds as the consequences of the split become clearer.
Pro-Brexit Conservatives have tended to oppose a long transition not only because it could be a first step towards reversing the referendum result, it would also mean several more years with the UK open to EU migration and paying into the common budget. The Tories would face fighting the next election -- due by 2022 -- open to the criticism that Britain hadn't really left the EU at all.

The next round of talks will begin about 5 pm Brussels time on Monday, as the EU tells the UK it needs more details of its position. EU officials have signalled they expect little movement, despite a series of UK position papers published during the last two weeks. Still, Brexit Secretary David Davis will ask his EU counterpart Michel Barnier to use "flexibility and imagination" to allow talks to move forward.

"For the UK, the week ahead is about driving forward the technical discussions across all the issues," Davis will say on Monday, according to his office. "We want to lock in the points where we agree, unpick the areas where we disagree, and make further progress on a range of issues."

His goal is to make enough progress by October, when EU leaders meet for a summit, to get approval for the talks to move on to trade - something EU officials currently say privately is unlikely.

The European Commission insists that some kind of progress the divorce bill, the issue of EU citizens' rights and a workable solution for the Northern Irish border has to be made before discussions move on to trade. A senior EU official on Friday downplayed the chance of any major advances this week in key areas such as the exit bill. German Chancellor Angela Merkel reminded Britain on Saturday that it had to settle its dues.

Bloomberg