United Kingdom, Oct. 17 -- Al Pacino was "shaken" by the passing of his The Godfather co-star Diane Keaton.

The 85-year-old actor has penned an emotional tribute to Keaton - who passed away last weekend from pneumonia at the age of 79 - and reflected on how his former partner had "lived without limits".

Pacino, who had an on-and-off romance with The First Wives Club actress from 1974 to 1990, told Deadline: "I am deeply saddened by Diane Keaton's passing.

"When I first heard the news, I was shaken. Diane was my partner, my friend, someone who brought me happiness and on more than one occasion influenced the direction of my life.

"Though over 30 years have passed since we were together, the memories remain vivid, and with her passing, ...