On Wednesday, Salman tweeted: "Directors of my film 'Lucky...' and 'Sanam Teri Kasam' churaud (stole) my song from Himesh (Reshammiya). Lovely song. Had selected it for 'Tere Naam'."
The song in question is titled "Haal-e-dil".
Asked about it, Sapru told IANS that it's the first song that appears in the film.
"Salman Khan is our mentor, so we do all our work keeping Salman informed about it. But as a project, we had not discussed 'Sanam Teri Kasam' with him. When we were discussing it and were showing everything that we have done in the film, 'Haal-e-dil' came up, and he said, 'This is my song!' He got a little upset about it," Sapru said.
Sapru says music director Himesh Reshammiya had told him that the song's tune was first finalised by Salman for the 2003 "Tere Naam", which also starred Bhumika Chawla.
"Not that we wanted to take this song, but when we were doing our music sitting with Himesh at that time, we finalised the first song of the film. There were two tunes to get finalised. But when Himesh said that this tune was finalised by Salman for 'Tere Naam', and he has kept another song that Salman could use it when he makes another tragic love story, we took this one."
"Salman has been our lucky charm since we started our career, and we were very clear that by hook or by crook, we want Salman's lucky charm in our film. So, we finalised that song."
The director said that the 50-year-old actor was "upset" but after seeing the song as part of "Sanam Teri Kasam", "it almost got tears to his eyes".
Also, Sapru feels Salman's tweet on the song has "so much of love".
"It's written by 'my directors'," he said.
"Sanam Teri Kasam", releasing on Friday, stars Telugu actor Harshvardhan Rane and Pakistani actress Mawra Hocane, who are foraying into Bollywood.