Nicola Sturgeon

Scotland’s parliament is poised to call for an independence referendum Tuesday, another headache for Prime Minister Theresa May as she battles to keep the country united just a day before triggering Brexit.

Lawmakers in Edinburgh are expected to vote in favor of Scottish leader Nicola Sturgeon’s plan for an independence referendum despite the prime minister’s last-minute appeals.

Sturgeon will then make a formal request for a referendum but she needs approval from the British government and parliament to do so and May has already said that “now is not the time.”

May will on Wednesday begin the process of ending Britain’s 44-year membership of the EU by invoking Article 50 of the European Union’s Lisbon Treaty, opening two years of negotiations.

Last year’s Brexit vote has spurred the independence campaign of Sturgeon, head of the ruling Scottish National Party (SNP), who argues that Scotland is being forced out of the European bloc against its will.

Both Scotland and Northern Ireland voted to remain in the EU, but they were outnumbered by voters in England and Wales who backed Brexit.

Most recent polls show support for independence is high but still short of a majority.

A survey by ScotCen published earlier this month showed support at 46 percent — its highest level since the yearly study began in 1999.

Sturgeon and May met in Scotland on Monday, with the prime minister reiterating that the time was not ripe for a referendum and describing the four nations of the United Kingdom as an “unstoppable force.”

The SNP leader has suggested an independence vote should be held by spring 2019 at the latest — before Britain leaves the EU.

Neither woman has expressed a willingness to compromise and the rift is unlikely to end before Article 50 is triggered.

Rejecting Sturgeon’s request would be politically risky for May, whose government is also trying to prevent the collapse of the power-sharing arrangement which governs Northern Ireland.

The Northern Ireland executive collapsed in January following a dispute between the two main parties, the Democratic Unionist Party and Irish nationalists Sinn Fein, which failed to reach a new power-sharing deal by a Monday deadline.

The British government has extended the talks and, if a resolution is not reached, fresh elections could be called or London could resume direct rule over Northern Ireland.

“In the absence of devolved government, it is ultimately for the United Kingdom government to provide for political stability and good governance,” Northern Ireland Minister James Brokenshire told parliament on Tuesday.

The fate of the province is one of the priorities set by the EU’s chief Brexit negotiator. “We will not stand for anything that weakens dialogue and peace in Northern Ireland,” Michel Barnier wrote in the Financial Times on Monday.

Despite May’s assertion, she will seek the best Brexit deal for all of Britain — including Scotland — she has failed to convince the SNP which has warned of the negative consequences of leaving the EU.

The economic uncertainty of Scotland outside the United Kingdom was a factor in voters rejecting independence in a 2014 referendum, but the SNP claims breaking away from the European single market would cost Scotland tens of thousands of jobs.

Scotland’s economic hand was strengthened on Monday when exploration firm Hurricane Energy announced the “largest undeveloped discovery” of oil in British waters, located west of the Scottish Shetland Islands.

But May also won a financial boost, with Qatar committing to invest £5 billion ($6.23 billion, 5.8 billion euros) in the UK economy within five years.

The announcement will allay fears of investors abandoning Britain when it leaves the EU and the European single market, which May has said is a necessary step to control immigration.

The prime minister made a plea for unity ahead of Britain’s historic EU departure.

“Now is the time when we should be pulling together, not hanging apart. Pulling together to make sure we get the best possible deal for the whole of the UK,” she told reporters.