Under Article 16, the United Kingdom and the EU can unilaterally decide to stop implementing parts of the protocol governing trade with the Northern Ireland if there are substantial practical problems or trade diversion.
The United Kingdom is ready to take unilateral action that would suspend custom checks on goods moving to Northern Ireland, says foreign minister Liz Truss ahead of talks with the European Union.
Truss is due to hold talks with EU Vice President Maros Sefcovic next week to resolve disagreements over post-Brexit trade arrangements for Northern Ireland, part of the United Kingdom which shares a land border with EU member Ireland.
To avoid politically contentious border checks between Ireland and Northern Ireland, Britain and the EU agreed Northern Ireland would effectively remain within the EU's customs union for goods, with checks taking place on goods moving between mainland Britain and Northern Ireland instead.
However, there has been some friction about how this applies in practice - especially for goods intended to remain within Northern Ireland - as well as the arbitration role of the EU's European Court of Justice.
"I want a negotiated solution but if we have to use legitimate provisions including Article 16, I am willing to do that," Truss wrote in The Telegraph newspaper.
"There is a deal to be done," she said, but added: "I will not sign up to anything which sees the people of Northern Ireland unable to benefit from the same decisions on taxation and spending as the rest of the UK, or which still sees goods moving within our own country being subject to checks."
Truss replaced David Frost as Britain's main Brexit negotiator in December, after he quit in protest at the broader direction of Prime Minister Boris Johnson's government.
Frost often raised the prospect of invoking Article 16 if talks stalled.