Confirmation of the Force India driver's move could come on Tuesday, a source close to Ferrari told BBC Sport.
Force India commercial director Ian Phillips told Radio 5 live on Monday: "We do expect a move will probably be made in the next 24 hours or so."
Fisichella would replace Luca Badoer, who has struggled as a replacement for the injured Felipe Massa.
Badoer, Ferrari's official reserve driver, was drafted in to replace the injured Felipe Massa after legendary seven-time F1 champion Michael Schumacher was forced to shelve his comeback plans.
Massa is recovering at home in Brazil after suffering a fractured skull in a crash during qualifying at the Hungarian Grand Prix in July.
The 28-year-old is targeting a return at the Brazilian Grand Prix on 18 October, but there is speculation that Massa will not be able to race until at least next season.
Ferrari are believed to have run out of patience with Badoer, who has qualified last at both of his races so far.
While Raikkonen won Sunday's race at Spa, Badoer trailed in last, nearly 48 seconds slower than the driver in front.
The Italian GP is on the 13 September, followed by Grands Prix in Singapore and Japan, before the teams head to Brazil.
Phillips added: "Nobody's asked us yet but I think it's pretty likely that somebody will make a phone call to (Force India team boss) Vijay Mallya over the next 24 hours or so asking if we would release him to Ferrari.
"I don't think they [Force India] have really got any options [but to release him].
"Ferrari being Ferrari, it's their home race at Monza, which is a place with a cauldron-like atmosphere, particularly for the Italians - seats will be thrown on the track if Ferrari aren't doing well.
"So they're going to have to put sombody in there who can basically run around with Raikkonen at the front of the field."
Ferrari team principal Stefano Domenicali said on Sunday: "With regard with what we are going to do for the next races we will tell you in the next three days.
"We are going to take all into consideration. It depends how the medical check-up that Felipe will do tomorrow (goes) and then we will put on the table all the different things. And then we will make a decision."
Fisichella told BBC Sport at the Belgian Grand Prix that it would be a "dream" to drive for Ferrari, but did not confirm that he had been approached.
The 36-year-old Italian's manager, Enrico Zanarini, told BBC Sport on Sunday that Ferrari had not been in contact.
"Nobody's been in touch," Zanarini said. "We find ourselves in a fantastic team with a great car for Monza because if the car is quick here it will be quick in Monza."
If he does move to Ferrari, Fisichella would drive only as a replacement for Massa - double world champion Fernando Alonso will switch to the team for 2010, although the Spaniard's move has not yet been confirmed.
Fisichella's contract with Force India runs out at the end of the 2009 season.
Force India would likely promote their reserve driver Vitantonio Liuzzi if Fisichella moved on.
By Adam Feneley
Motorsport Engineering
www.motorsportengineering.blogspot.com
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