A Plaid Cymru AM has said she is "not entirely comfortable" with electoral pacts but they are the "right thing to do" in the general election.
Helen Mary Jones said it "won't be easy" for candidates to stand down if an agreement with other pro-remain parties is reached.
Discussions are ongoing between Plaid, the Liberal Democrats and Green Party.
The three parties struck a deal in the Brecon and Radnorshire by-election in August, which was won by the Lib Dems.
Despite reports the parties have reached a wider electoral pact for the election on 12 December, sources have said the discussions within and between the parties continue.
Ms Jones, AM for Mid and West Wales, said: "It's not always easy to co-operate with people from different parties and obviously we've got different views... But I'm not entirely comfortable, I don't think anybody is.
"This is about whether we can return enough MPs to prevent Brexit, which would be so disastrous for Wales.
"It won't be easy for the party activists who've worked their socks off in constituencies, it won't be easy if we have to ask some candidates who've already been chosen and have already begun to work to stand down.
"But this is so serious. There is no form of Brexit that isn't going to be really damaging to our economy, to our rural communities, to our environment, to the future of our young people, and in this election, just this election, we have to do whatever we can to stop that disaster."
On Friday, Prime Minister Boris Johnson rejected the idea of working with the Brexit Party during the election after Nigel Farage called for him to drop the new Withdrawal Agreement deal in a "leave alliance".
Labour leader Jeremy Corbyn has ruled out the idea of entering electoral pacts with other parties, while First Minister Mark Drakeford said he was "instinctively not attracted" to the idea.