Gulzar Thursday wrote the letter titled ""Mujh Se Naraz Na Hon" to the founder and organiser of the Karachi Literature Festival, Ameena Saiyid, reported Dawn.
He said it was during his visits to his birthplace Dina and to poet Ahmed Nadim Qasmi's gravesite that he felt "uneasy in the chest".
When the discomfort continued, he decided to go back to Mumbai -- "... a familiar terrain to meet such contingencies".
Gulzar and Bhardwaj had gone to Pakistan Monday to record a qawwali for the upcoming Bollywood film "Dedh Ishqiya" and the lyricist was also expected to attend the Karachi Literature Festival.
Gulzar said that "while at Lahore, I had taken the opportunity to visit Dina to have a look at the house where I was born and spent my teens and of course the Qaber of my late guru and mentor Ahmed Nadeem Quasmi to pay my respects. I was moved very much by these two visits. As ill-luck would have it, I felt very uneasy in the chest. The uneasiness subsided temporarily at the recording studio".
"We were recording a song for (filmmaker) Vishal with Pakistani singers. The discomfort returned when I reached the hotel. It was 2 a.m. Vishal postponed the recording for a later date some time in March and we impulsively decided to return to Mumbai, which being a familiar terrain to meet such contingencies.
"...I had come fully prepared for The Karachi Literary Festival. But this mishap has disappointed me very much."
He added: "I am awfully sorry for this, which is beyond my control. With very best wishes for a very successful festival..."
"Dedh Ishqiya", a sequel to the 2010 critically acclaimed film "Ishqiya", features Arshad Warsi and Naseeruddin Shah along with Bollywood's dancing diva Madhuri Dixit in key roles.