The Democratic Unionists and the Ulster Unionists said they have ruled out an overall pact for Northern Ireland in the General Election.
Party leaders Arlene Foster and Robin Swann held talks about the potential of joining forces in a bid to return the maximum number of unionist MPs to Westminster.
But despite both parties already deciding against splitting the unionist vote in some crunch constituencies, the pair said they could not agree on an overall formal pact.
In a joint statement from Ms Foster and Mr Swann, they said they would continue discussions about closer unionist co-operation in the time ahead.
"Both of our parties want to see the strongest possible vote for pro-union candidates standing in all of the 18 constituencies across Northern Ireland," they said.
"We are committed to work co-operatively to do all we can to maximise voter turnout.
"While our parties have not concluded any formal pact arrangements on this occasion we are resolved to continue discussions in the interests of better unionist co-operation beyond this election period."
The DUP has already announced it is not standing in Fermanagh and South Tyrone, where it is giving the UUP's Tom Elliott a free run against Sinn Fein.
An identical gesture helped Mr Elliott take the seat from Sinn Fein's Michelle Gildernew last time around on a margin of just over 500 votes.
Likewise, the UUP has declared it will not field a candidate in North Belfast, where it is urging unionists to vote for the DUP's Nigel Dodds.
In what will be one of the most closely-watched battles of the June 8 poll, John Finucane, a son of murdered Belfast solicitor Pat Finucane, is standing for Sinn Fein.
In the last general election, the DUP and UUP agreed pacts in four constituencies.
A separate push for an anti-Brexit electoral pact in the region was left in disarray over recent weeks after pro-Remain parties failed to strike a deal.
SDLP leader Colum Eastwood suggested any agreement was doomed after the Green Party announced it would not take part.
The Alliance Party had already scotched the idea from the outset, leaving only the SDLP and Sinn Fein as potential partners.
Mr Eastwood said he would not be part of a pact that only involved two parties.