The actor chosen for the role will provide the voice for the lead character in the Hindi version of the Disney film, which releases in India in December.
According to The Hindustan Times, a source said: "Both actors have been approached and are considering the offer. Now it depends on who will be available and the amount they charge.
"But it will be one of the two for sure as the makers are convinced that both their voices suit the character of Ralph the best."
Barfi! star Ranbir is said to be the favourite for the role, but debutante actor Arjun is also recognised for his popular appeal.
"At this point, Ranbir stands a very high chance. But while Arjun is just a film old, he has gained enough popularity for the makers to want to have him on board," the insider added.
"Also, they have a strong youth appeal, which will pull in more crowds. In the past too, many big stars have given their voices for the Hindi release of Hollywood films and it has worked well."
Other stars who have leant their voice to animated films include Shah Rukh Khan in the Hindi version of The Incredibles, titled Hum Hain Lajawaab, and Akshay Kumar, who dubbed the voice of Optimus Prime in the sci-fi film Transformers: Dark of the Moon.
Watch the trailer for Wreck-It Ralph below: