Britain will threaten this week to deviate from the Brexit deal unless the European Union shows more flexibility over Northern Ireland, one UK and three EU sources told Reuters.
David Frost, the British minister who leads Brexit negotiations, is preparing to announce a significant potential change on the protocol that could have far-reaching consequences for the relationship with the EU, one of the sources said.
The British government declined immediate comment.
Brussels expects Mr Frost will push for a deviation from the protocol unless the EU agrees to compromise, an EU diplomat said.
A third source, a senior EU official, said Britain would caution the EU that unless Brussels can reach an agreement, then unilateral measures would be possible by using Article 16 of the protocol.
"It will be a plea for more talks with the EU combined with a threat," said the senior EU official.
Britain is expected to go beyond its demands for changes to veterinary rules. The senior EU official and a second EU diplomat said that London would seek to have the European Court of Justice (ECJ) removed from the arbitration process.