The board of the Bradford-based grocer has already recommended a £6.3bn offer from Oppidum Bidco, the bid vehicle set up by US-based Fortress.
Apollo had previously been mulling its own rival bid but in a statement this morning said as a consequence of these discussions with Fortress, it confirms that it does not intend to make a separate offer for the FTSE 100-listed other than as part of the consortium.
The offer from Fortress, which has funding backed by the Canada Pension Plan and US billionaire Charles Koch's real estate business, is pitched at 254p per share, around a 42% premium to the closing price on 18 June.
Morrisons rejected an earlier bid from private equity group Clayton, Dubilier & Rice’s (CD&R) at 230p a share.
Fortress, which is owned by Japanese investment colossus SoftBank, has said it has no plans to sell any Morrison stores, and “will support Morrisons and its employees in executing management's existing strategy”.
The shares were broadly flat following the announcement.
Analyst Sophie Lund-Yates at Hargreaves Lansdown said: “From a shareholder perspective this is disappointing, because it takes the heat out of a potential bidding war, meaning the cash offer already on the table is less likely to get pushed upwards.”
With Morrisons shares having risen above 265p since the Fortress bid, she added that if Apollo can get in on the deal without making a higher bid “why wouldn’t it?”
“Increasing private equity activity in London in recent months means there could be other raised arms in the bidding hall, but for now, Morrisons is back to courting a single suitor.”
The shares fell a couple of pennies to just above 260p in early trading on Tuesday before coming off a little.
**Adds share price and broker quote**