Flintshire council has said it was in the public interest to discuss joining up with Wrexham in a bid to cut costs.
But Wrexham council has already issued a statement saying it was unlikely to pursue a possible merger.
Meanwhile, Conwy has voted to open talks with Denbighshire as Welsh authorities are urged to join forces.
It comes as new Public Services Minister Leighton Andrews says voluntary mergers would give "greater certainty" as the Williams Commission said the number of councils should be halved.
Flintshire council leader Aaron Shotton said: "The council was united in prioritising the protection of local services to the communities of Flintshire and was mindful that if services could be protected, and costs reduced through mergers of services between Flintshire and Wrexham, then it would be in the public interest to explore the benefits of a merger."
But he added the Welsh government needed to give more explanation over the costs and benefits of the merger before it went ahead.
However, last week, Wrexham council issued a statement saying that following a consultation with councillors, it did not want to merge with Flintshire.
Wrexham council leader Neil Rogers said: "Members agreed unanimously that the county of Wrexham should remain in its current form as it is large enough to stand alone."
In north Wales, Conwy council has voted to begin talks with Denbighshire council over a merger.
Councillors at a special meeting said it was "an amber light" in the process after Denbighshire councillors made the same move last week.
The Welsh Local Government Association has claimed mergers could cost up Â£200m.
Mr Andrews has said voluntarily merged councils could be up and running from 2018.
A north Wales council welcomes the possibility of a voluntary merger with its neighbour but it says it is unlikely to pursue a link-up.