There should be a general election if the devolved parliaments reject the final Brexit deal, Wales' first minister has said.
Carwyn Jones said the withdrawal deal brokered by the UK government should be approved in Westminster, Edinburgh and Cardiff.
MPs have been promised a meaningful vote on the deal.
The Welsh Government confirmed AMs will also get a vote, but AMs cannot force UK ministers to act or veto Brexit.
Welsh Secretary Alun Cairns said he did not see the logic behind Mr Jones's argument.
Mr Jones's comments come as pressure builds within Labour for the party to back a further EU referendum.
He told BBC Wales that Labour needed to agree its policy no later than November.
The planned assembly vote on the Brexit deal would be symbolic and not legally binding.
Mr Jones said "the time was not right yet for a second referendum", but there could be circumstances where there is no other way to resolve a political stalemate.
"For me, the next step is to see whether a deal can be supported by - for me - parliaments plural: Westminster, Edinburgh and Cardiff," he said.
"If that doesn't happen, then I don't see any other alternative than a general election where Brexit will be the main issue."
"If there's an inconclusive result as a result of that general election, well, how then do you resolve the issue without going back to the very same people who took the decision in the first place?
"I think at that point you are talking about the potential for a second referendum."
'A long-way from a done deal'
Asked whether that meant calling a general election if the assembly votes against the Brexit deal, he said: "In my view, yes.
"I think it's important to get agreement across the UK, but the major test I suppose will be getting agreement within the UK parliament itself and that is a long way from a done deal at the moment."
There are calls for Labour to discuss proposals for another referendum at its party conference in Liverpool this weekend.
Candidates vying to succeed Mr Jones as Welsh Labour leader have backed calls for a new referendum on the final Brexit deal.
Mr Jones said Labour "needs to have a debate", but that there were deeper divisions in the Conservative Party.
He said he was "nervous" about calling for a second referendum "in the wrong circumstances".
"Why? Because it makes you look as if you won't accept the result and I think that's a difficult position."
He added: "Clearly there needs to be a very established position by October or November."
The Welsh Government - which is hiring 198 extra civil servants to work on Brexit - has an "enormous" task to prepare for leaving the EU, Mr Jones said.
Mr Cairns, the UK government's Welsh secretary, said he did not "quite follow the logic" of the first minister's comments.
He said: "There is separate legislation that would lead to a general election and there are also 40 Welsh MPs who will have a vote on that meaningful vote that will be tabled in the House of Commons".