A government source said Sunak had agreed the terms with European Commission President Ursula von der Leyen as they met in London.
The agreement marks a high-risk strategy for Sunak who has been looking to secure a compromise and improve relations with Brussels — and the US — without sufficiently angering the wing of his party most wedded to Brexit.
The new agreement is expected to ease physical checks on goods flowing from Britain to Northern Ireland, and give the province’s lawmakers a say over the EU rules it has to implement under the complicated terms of Britain’s exit from the bloc. London could also set some tax and state aid rules.
Its success could hinge on whether it convinces the Democratic Unionist Party to end its boycott of Northern Ireland’s power-sharing arrangements. The deal seeks to resolve tensions caused by the 2020 post-Brexit arrangements governing Northern Ireland, a British province, and its open border with EU member Ireland. It remains to be seen, though, whether it will go far enough to end political deadlock in Northern Ireland.