The British government dramatically escalated a fight with the European Union on Tuesday (local time) by saying it will pass a law to change the trade treaty signed by the two sides less than two years ago.

Britain says its move to scrap parts of the legally binding treaty is an insurance policy in case it can’t reach agreement with the bloc to end a long-running dispute over post-Brexit trade rules.

The threat of legislation is sure to rile the EU, which accuses Prime Minister Boris Johnson of trying to wriggle out of a deal that his government negotiated and signed as part of the UK’s exit from the bloc in 2020. It raises the spectre of a trade war between Britain and the 27-nation bloc that is – even after Brexit – its major economic partner.

Foreign Secretary Liz Truss told lawmakers in the House of Commons that the move “is consistent with our obligations in international law”.

Truss said the bill will be published in the coming weeks, and she hopes to keep up talks with the bloc in the meantime.

“Our preference is to reach a negotiated outcome with the EU,” Truss said.

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Britain says post-Brexit trade rules are hurting the economy and undermining peace in Northern Ireland, the only part of the UK that shares a border with an EU member state.

The Democratic Unionist Party, Northern Ireland’s biggest unionist party, is blocking the formation of a new regional government in Belfast until the checks are scrapped.

Under power-sharing rules set up as part of Northern Ireland’s peace process, a government can’t be formed without the co-operation of both unionist and nationalist parties.

The British government agrees that the trade regulations, known as the Northern Ireland Protocol, are destabilizing a peace agreement that relies on support from both Protestant unionist and Catholic nationalist communities.

While the DUP wants the Protocol scrapped, most other parties in Northern Ireland want to keep it, with tweaks to ease the burden on businesses.

Johnson says his government wants to fix, rather than scrap, the arrangements, using technology and trusted-trader programmes to create a check-free “green lane” for goods destined for Northern Ireland that are at little risk of entering the EU.

“There are too many companies, including major supermarkets, at the moment who have no stores in the Republic of Ireland, who are moving their products from their depots in Great Britain into Northern Ireland for sale and consumption in Northern Ireland, but going through checks as if they were going into the EU,” said the UK's Northern Ireland Secretary, Brandon Lewis.

The British government hopes its threat of legislation – which would take months to pass through Parliament – will increase pressure on the EU to compromise.

The bloc insists the legally binding Brexit treaty can’t be renegotiated, though it is willing to be flexible about how it is implemented. The EU could hit back at Britain with legal action, and potentially trade sanctions, if Britain does not back down.

Irish Foreign Minister Simon Coveney said Monday that Britain’s stance “calls into question” the entire post-Brexit trade agreement that the UK and the bloc hammered out in months of rancorous negotiations.