Mr Holley said they had pulled out all the stops to try and secure a headline act to replace Neil Diamond who has had to cancel in the wake of medical issues.
"We are leaving no stone unturned and we have made offers," he said, adding that when it came to securing an artist there were "so many people to talk to".
It could take up to six months to get an artist signed, through negotiations with promoters, agents and management teams.
"And we are trying to do it in six weeks.
"It is one of those adverse things that can happen in the business," Mr Holley said.
The organisers had been nevertheless buoyed by the support and goodwill they had received in the wake of the news that Neil Diamond's onset of Parkinson's disease.
"People have been very good about it — they know we've been left short."
SEL events manager Garry Craft said on the Mission Facebook site that they had been in discussion with two artist possibilities.
"This process is not a simple one and involves a lot of people making decisions that we have no control of," he said.
"The process to secure international artists requires schedule changes, time zone impacted correspondence and with Hawke's Bay being quite a distance from the world's music hubs we need at few more days to pull this together."
He said a lot of commitment went into presenting an annual Mission Concert and like an overwhelming number of Concert Club members the organisers wanted to see that continue.
Mr Holley said everything that could be done was being done but for the sake of hopeful concertgoers wanting to finalise plans they "can't drag this on".
Accordingly, Friday would see the announcement of the "final position".
