LONDON (AP) — Britain published its opening demands for trade talks with the European Union on Thursday, delivering a blunt threat to walk away from the table if there is no progress within four months.

The two sides appear headed for a rocky first round of negotiations as they try to forge a new relationship following the U.K.'s departure from the now 27-nation bloc.

Britain and the EU both say they want to reach a free trade agreement, but have starkly divergent views on how it should be overseen and what constitutes fair competition between their two economies.

The EU says Britain must agree to follow the bloc's rules in areas ranging from state aid to environmental protections, and give European boats access to U.K. fishing waters, if the two sides are to strike a good deal.

But the U.K. is demanding the right to diverge from the bloc's rules in order to strike new trade deals around the world and bolster the British economy.

"In pursuit of a deal we will not trade away our sovereignty," Michael Gove, the minister in charge of Brexit preparations, told lawmakers in the House of Commons.

Britain's negotiating mandate insists that "we will not agree to any obligations for our laws to be aligned with the EU's, or for the EU's institutions, including the Court of Justice, to have any jurisdiction in the U.K."

That conflict will be one of the big hurdles in talks, which are due to begin Monday in Brussels.

Britain left the EU on Jan. 31 but remains bound by the bloc's rules until a post-Brexit transition period ends on Dec. 31. A divorce agreement between the two sides allows for the transition to be extended for two more years, but British Prime Minister Boris Johnson insists he will not agree to that.

Johnson's Conservative government says the U.K. will be leaving the bloc's structures — including its single market for trade in goods and services — as of Jan. 1, 2021.

Britain hopes by then to have a trade agreement with the bloc similar to the one struck between the EU and Canada. Such a deal would eliminate tariffs and quotas on trade and goods, but it's less clear what it would mean for the services sector that makes up four-fifths of Britain's economy.

The EU-Canada deal also took years to strike — now the two sides have just months.

Britain's negotiating guidelines insist that there is "limited, but sufficient time" to get a deal. The document says a "broad outline" of an agreement should be done by June. It warns that if there is not sufficient progress by then, the U.K. could walk away and focus on "domestic preparations to exit the transition period in an orderly fashion."

Britain's tough talk is unlikely to impress EU negotiators, who already accuse Johnson of trying to water down commitments Britain made in the divorce deal that paved the way for the country's seamless departure on Jan. 31. That withdrawal agreement dealt with three broad issues — citizens' rights after Brexit, Britain's liabilities after 47 years of service and the need to maintain a frictionless border between EU member Ireland and Northern Ireland, which is part of the U.K.