British Prime Minister Boris Johnson said on Monday the government needed an "insurance" option to unilaterally scrap post-Brexit trade rules for Northern Ireland, raising the risk of a trade war with the European Union.
Johnson says the EU must make concessions on the rules - known as the Northern Ireland protocol - to win over the province's unionist community loyal to the United Kingdom, and has threatened action that the bloc says could start a trade war.
The prime minister said plans to propose legislation to rewrite parts of the protocol were only necessary in case talks with the EU on improving its operation failed.
"We would love for this to be done in a consensual way with our friends and partners, ironing out some of these problems," Johnson told reporters. "But to get that done, to have the insurance, we need to proceed with a legislative solution at the same time."
Johnson agreed to the protocol in 2019 to allow Britain to leave the EU's single market and customs union without controls being re-imposed on the border between the Irish Republic and Northern Ireland, a vital part of the 1998 Good Friday peace deal that ended three decades of violence.
But the plan effectively introduced a customs border between Britain and Northern Ireland, incensing many unionists.
The dispute has stymied another part of that peace deal - power-sharing between Sinn Fein and the Democratic Unionist Party it beat in the election. The DUP has blocked power-sharing because of its opposition to the protocol.
Johnson said all five of Northern Ireland's main parties had problems with the protocol.
"None of the parties - I spoke to all five parties just now - not one of them likes the way it's operating, they all think it can be reformed and improved," he said.
Earlier, Sinn Fein President Mary Lou McDonald said her party had a "fairly tough" meeting with Johnson in which they told him taking unilateral action over post-Brexit trade rules for Northern Ireland would be wrong.
McDonald, whose party seeks a united Ireland and is now the region's largest after an election this month, said Johnson did not give details of any proposed legislation which would effectively ditch parts of the protocol.
"We've had what we would describe as a fairly tough meeting with the prime minister," McDonald told reporters following the talks with Johnson in Northern Ireland.
"We have said directly to him that the proposed unilateral act of legislating at Westminster is wrong. It seems to us absolutely extraordinary that the British government would propose to legislate to break the law."
The EU has said that renegotiating the protocol is not an option but that it is open to joint work to bring long-term certainty.
Speaking to reporters, DUP leader Jeffrey Donaldson said he hoped the government would do the right thing and help restore a consensus in Northern Ireland. "It's actions that I will judge these things on, not just words," he said.