England and Scotland will tomorrow sign a contract with basketball's world governing body FIBA that will formally merge them as Great Britain from 2016.
FIBA secretary general Patrick Baumann has confirmed the deal has been agreed despite Wales voting against a merger and opting to remain independent.
"This contract will be signed on Sunday," Baumann said.
The home nations have played under one banner since 2006, part of a temporary arrangement that saw British Basketball formed as an umbrella organisation with the goal of getting teams into the London Olympics.
FIBA last year awarded Britain the host nation place on the condition that England, Scotland and Wales make a decision on whether to retain the structure beyond the 2016 Olympic cycle, or go their separate ways once again.
A decision had been due by June 30, but while England and Scotland voted in favour, Wales came out in opposition, with the board of Basketball Wales saying they had seen little benefit from being a part of British Basketball.
Baumann said today that though he respects their decision he believes it is wrong and they will eventually see the British Basketball project is "unstoppable" as England and Scotland control such a large part of the game in the country.
"You have something that is not just a large majority, but almost unanimity wanting to maintain a British program beyond this term and to go on and be successful for the good of the game," Baumann said.
"I think we will be able to persuade Wales to join this party...
"Despite the Welsh negative decision we still took the view to sign the contract with England and Scotland, because I think this is going to be unstoppable."
From 2016, England and Scotland will cease to hold individual membership of FIBA and will hold one joint membership as Great Britain.
"We always knew England would be in favour of the British concept given their status within that concept, but what Scotland has decided has been extraordinary," Baumann said.
"They have relinquished their membership in favour of a British program and in 2016 they will no longer be a member of FIBA directly but they will be part of a British federation which in turn is a member of FIBA.
"They've given up something extremely important to them for the benefit for the game in this country, and so did England, and they're covering about 95% of the basketball in this country.
"We have to respect the decision of the board of Basketball Wales, but I think this is unstoppable."
While there are English and Scottish players in both the British men's and women's teams, there are none from Wales.
That was one of the reasons cited by Basketball Wales when it voted against a merger, with the board saying they did not want to close the door on their players playing in international competition going forward.
But Baumann said he did not see the value in playing at low level competition for the sake of it.
"Every stakeholder who is giving up something needs to put on the table what they want in return," he said. "But if you are maintaining independence just for the sake of playing in Division C in Europe, I'm sorry, that's not the right argument, and it is not even supported by the government in Wales.
"There's a role for everyone. It doesn't mean there won't be any Welsh basketball players. It's just about finding the right pathways for Welsh players to join the British program and not get lost between England and Scotland."