Beckham was a key figure in the bid team that helped secure the Games in 2005 and has been one of the most visible celebrity supporters of it in the years since.
"He was not only alongside us when we won (the right to host the Olympics), he was alongside us when we threw our hats in the ring," Coe told Sky Sports News.
Many had anticipated his hard work for the cause would help him win one of the three over-age player slots in Team GB's football team but manager Stuart Pearce opted not to take the former England captain.
He picked his 18-man squad on exclusively footballing reasons and indicated he had never been leant on to pick Beckham. Since his omission was revealed, speculation has mounted over what role Beckham might play.
Coe admitted that had already been discussed and expects to make the nature of the 37-year-old's responsibilities clear soon.
He continued: "He's a north-east London boy, he knows what sports means in those areas, and he's probably one of our longest and truest supporters.
"We are scoping a role for him at the moment. I actually spoke to him over the course of the weekend. We're working on it, but you'll have to watch this space."
Coe also made it clear that Beckham's task would not be a spurious one or a mere marketing opportunity.
"He will be in London with us and he will have two very clear roles within the Games," said Coe. "He will be more than an ambassador given what he has done, the commitment he has given and the amount of time he has spent with us in London on this project."