The United Kingdom may deviate from the Brexit deal this week unless the EU shows more flexibility over Northern Ireland, the sources told Reuters on Monday.
UK Prime Minister Boris Johnson, who signed a deal in 2020, was concerned that the protocol could prevent British food staples such as sausages going to Northern Ireland.
The British minister for Brexit negotiations David Frost is going to announce a significant potential change on the protocol that could have far-reaching consequences for the relationship with the EU, one source
"Frost is due to update parliament on Wednesday about Northern Ireland and Brexit, and will also present a paper on Brexit to lawmakers," the report says.
According to a senior EU official, the UK could use unilateral measures unless an agreement is reached.
"It will be a plea for more talks with the EU combined with a threat," said the senior EU official. "But we will not agree to the reopening of the Irish protocol."
Britain is also expected to go beyond its demands for changes to veterinary rules.
The so-called Northern Ireland Protocol aimed to prevent Brexit from disrupting the peace brought to Northern Ireland by the US-brokered 1998 peace deal that ended three decades of conflict between Irish Catholic nationalist militants and pro-British Protestant "loyalist" paramilitaries in which 3,600 people were killed.