Ferguson also confirmed that Wayne Rooney is back in training ahead of Monday's derby against Manchester City at Old Trafford.
The England striker, 27, has missed United's last two matches with a groin injury sustained on international duty.
Robin van Persie's goal trail
Van Persie scored 23 times in his first 31 games in all competitions for Manchester United, including 11 goals in 11 matches between 28 November and 20 January.
He has gone nine games without scoring for United - four in the Premier League, two in the Champions League and three in the FA Cup - since 10 February.
But he has scored three times for Netherlands in World Cup qualifiers in the meantime - with a goal in the 3-0 win over Estonia on 22 March, and two more in the 4-0 victory over Romania four days later.
Defenders Nemanja Vidic and Jonny Evans remain doubts with knocks picked up during at Sunderland, but Ferguson is hopeful that both will resume training soon.
He said: "Wayne and Rafa have started training which is good news. We hope they will be fine by Monday. Jonny Evans and Nemanja Vidic are not there yet but hopefully they will start tomorrow (Friday) or Saturday morning."
Premier League leaders United are 15 points ahead of second-placed City going into Monday's match.
Ferguson added: "It's a derby game with a difference from years ago. It's far more important. We have to get used to playing Manchester City in big games."
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