The Liberal Democrats have said they have entered a pact with Plaid Cymru and the Greens not to run candidates against each other in a number of seats in the election on December 12.
Details of the arrangements, thought to cover 60 to 70 constituencies, by the three pro-Remain parties will be announced at a press conference on Thursday by the Unite to Remain group, which brokered the deal.
It followed the agreement earlier this year in the Brecon and Radnorshire by-election, where the Lib Dems took the seat from the Conservatives after the other two parties stood aside.
Lib Dem leader Jo Swinson said: “We are delighted that an agreement has been reached. This is a significant moment for all people who want to support remain candidates across the country.”