British Prime Minister Boris Johnson has said the UK will have a "necessity to act" if the EU is unwilling to reach a compromise in the deepening crisis over the Northern Ireland Protocol.
Mr Johnson - who travels to Belfast tomorrow for emergency talks with the Northern Ireland parties - said his government remained open to "genuine dialogue" with Brussels.
But amid fears of a looming trade war, he said that if there was no movement on the EU side, the government will set out its "next steps" in a statement to parliament "in the coming days".
His warning comes amid reports ministers could table emergency legislation as early as this week to override the Protocol which requires customs checks on goods moving from Great Britain to Northern Ireland.
EU leaders have said such a move would violate Britain's international treaty obligations under the Withdrawal Agreement signed by Mr Johnson and would lead to retaliatory measures.
In the meantime the power-sharing institutions in Northern Ireland remain suspended with the DUP refusing to join Sinn Féin in a new Executive or to allow the election of a Speaker to the Assembly unless there is fundamental change to the Protocol.
Writing in the Belfast Telegraph, Mr Johnson said there was still a "sensible landing spot" where the interests of all sides are protected - including the integrity of the EU single market, which the Protocol is designed to maintain.
However he said that would require movement on the part of the EU.
"We have been told by the EU that it is impossible to make the changes to the Protocol text to actually solve these problems in negotiations - because there is no mandate to do so," he said .
"We will always keep the door wide open to genuine dialogue. There is without question a sensible landing spot in which everyone's interests are protected.
"I hope the EU's position changes. If it does not, there will be a necessity to act.
"The government has a responsibility to provide assurance that the consumers, citizens and businesses of Northern Ireland are protected in the long-term.
"We will set out a more detailed assessment and next steps to Parliament in the coming days," he wrote.
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Unilateral moves will destabilise NI - Taoiseach
Earlier the Taoiseach called for the British government to engage professionally and sincerely with the European Commission in relation to resolving issues around the operation of the Northern Ireland Protocol.
"The [European] Commission came forward with measures that would reduce significantly the impact of the operation of the Protocol and, in my view, did not get a substantive response from the British government."
Mr Martin said unilateralism does not work and will not work. And as co-guarantors of the Good Friday Agreement, he said the British and Irish governments need to work together to resolve issues with the Protocol.
He added that unilateral moves by the British government will destabilise the situation even further and undermine the spirit of the Good Friday Agreement.
Mr Martin said there is an urgent obligation on the British Prime Minister Boris Johnson to engage with the European Commission in a meaningful and professional way to resolve issues that have been raised.
Mr Johnson will travel to Northern Ireland tomorrow to meet with the political parties.
Earlier today, the Minister for Foreign Affairs Simon Coveney raised concerns that the British government could legislate unilaterally on the Protocol to address the concerns "of one community" in Northern Ireland.
He said it has indicated this approach could be taken this week "if the EU doesn't give them everything they want".
Speaking on Sky News, Mr Coveney warned it is "not the way to approach a problem with a neighbour and a friend" and said it would create huge problems for Ireland and "unnecessary tension" with the EU.
Mr Coveney said briefings this week from the British government had raised a "real red flag" in Dublin and Brussels.
"The British government is now threatening to break international law, to break a treaty that they signed with the EU and they designed with the EU and that they ratified in the House of Commons and in doing so potentially creating huge problems on the island of Ireland," he said.
He added that while issues relating to the implementation of the Protocol need to be resolved, there are concerns within the unionist community in particular that need a comprehensive response.
"The way to do that isn't for the British government to act unilaterally and to brief against the EU in the way
they have this week, encouraging the PM to act like he has acted on Ukraine in relation to the Protocol and urging him to rip it up," he said.
"That kind of aggressive language does nothing to move us forward on what is a difficult issue."
He said the EU has not threatened anything but just wants partnership with the UK to work together to resolve the issues around the Protocol.
"The last thing the EU wants, the last thing that Ireland wants, is tension with the UK, particularly at the moment with what is happening in Ukraine, Russian aggression, and the need to work together on the international stage," Mr Coveney said.
He referred to a "difficult and polarising election" in Northern Ireland and how the challenge now is to listen to all communities to ensure the agreements signed in the past are applied with "flexibility and pragmatism" to respond to all concerns.
Sinn Féin Vice President and its Stormont Assembly leader, Michelle O'Neill, said: "Any threat of unilateral action by the British government to denounce the Withdrawal Agreement, or disapply the Protocol would be reckless.
"Walking away from international obligations would also represent an appalling attack on the international rule of law. "
She added: "Only through joint agreement with the EU can solutions to problems or concerns be resolved.
"I will be telling Boris Johnson that unilateral action deepens political instability and economic uncertainty and must not happen."
Labour Party leader Ivana Bacik said that a move by the British government to act unilaterally on the Protocol would "clearly be a breach of international law".
She said that her party is deeply concerned about the prospect, as Anglo-Irish relations are "at a particularly low point".
"The real danger for all of us, particularly someone in my generation remembering the Troubles, the real danger is that we see any sort of breakdown of the peace process that led to the Good Friday Agreement," she said.
