The Manchester United boss says he is very pleased to sign the Dutchman and claims he now has four strikers to rival his famous 1999 quartet.
The Dutchman is expected to arrive in Manchester on Wednesday to agree personal terms and undergo a medical with the Red Devils after they agreed a 24 million pound fee with Arsenal.
Sir Alex dismissed fears that he would have a selection headache following Van Persie's arrival, drawing comparisons between the side and the attacking line that fired United to the 1999 treble.
"Rooney and Van Persie are two fantastic players and it's great to have both of them," he told reporters. "What it gives us is more strength and combinations up front. Going back to the 1999 season, we had Yorke, Cole, Sheringham and Solskjaer, the four best strikers in Europe.
"We're getting towards that now with Wayne, Robin, Chicharito and Danny Welbeck. It's a fantastic collection of players. I just hope I pick the right combinations. It's great to have a player of Van Persie's quality to come into the squad as it is. I'm really pleased."
The 70-year-old also revealed that the deal is to be sealed imminently and that he expected the Dutchman to be available for United's Premier League opener against Everton on Monday evening.
"We are delighted with [the Van Persie deal] of course," he added. "He's not signed yet, but a fee has been agreed. He's on his way up from London and will have a medical later this [Wednesday] afternoon. Hopefully that goes according to plan.
"His agent is also in discussion with David Gill. Hopefully all these things will be tied up by the end of the day. But sometimes medicals take a little longer and it may carry on until tomorrow. But I'm sure he will be available for Monday's game."
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