The EU states will need Britain to formally reply to the offer of a three-month delay before launching a “written procedure”, whereby governments will have 24 hours to accept or reject.
“We can only launch the written procedure when we have the agreement of the UK government on the text,” a senior EU official said.
Boris Johnson is obliged by legislation passed by parliament last month, the Benn Act, to accept an extension once offered.
The PM will respond to the EU’s delay offer once he has reviewed the details, his spokesman said on Monday.
