Xbox boss Phil Spencer has explained the delay in getting Activision Blizzard's back catalogue added to Xbox Game Pass, and blamed the hold-up on the lengthy and difficult process of sealing the deal.

Speaking on the Official Xbox Podcast, Spencer acknowledged the recent suggestion by Activision Blizzard that it would take until 2024 to get its games added to Microsoft's subscription service, and discussed why there wasn't going to be a big drop of games sooner - as happened when Microsoft bought Bethesda.

Spencer even noted there had been "a lot of uncertainty" in the buyout process for Microsoft - right up until the deal was finally approved by the UK's regulator, the Competition and Markets Authority, last week.

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"The regulatory process took so long - and frankly there was a lot of uncertainty in that process up until really a week before we closed, or the week of, when the CMA finally came down to their decision," Spencer said.

"We weren't able to get in and work with [Activision Blizzard] on that back catalogue work. Now the deal has closed we are starting that work, but there is work."

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Xbox Game Pass subscribers should - as previously suggested - expect a dollop of Activision Blizzard titles to arrive in 2024, Spencer continued. But there's no "secret" stealth drop of games planned to arrive sooner - as some rumours on the internet have suggested.

"[They] did put out something that talked about 2024, I think that's accurate," Spencer said. "I would love it if there was some kind of secret celebration drop coming in the next couple of weeks. There's not."

Being transparent with players who already have plans to purchase this year's Call of Duty: Modern Warfare 3 is also important, the Xbox boss said.

"Definitely when we think about the new games that are there, I would be straight with people if we're going to put them in the subscription this year - I'd tell people.

"I know there's definitely some disappointment about that, this aquisition is long-term so the fact we're not hitting day one with a bunch of games dropping into Game Pass is a little bit of a downer but I'm very excited about the future."

Activision Blizzard is the home to a host of well-known game franchises which fans are hoping to see pop up on Xbox Game Pass at some point in the future. This includes the Crash Bandicoot series and Tony Hawk's Pro Skater, as well as Call of Duty. There's also Guitar Hero and Skylanders - though sourcing physical extras for these franchises might prove a problem.

Elsewhere on the podcast, Spencer also discussed Call of Duty's future, and how Microsoft won't use timed exclusivity to make people buy Xbox consoles.