When did Mikhail Gorbachev used the phrase "if not me who if not now when"?

Question

I am wondering if he used this phrase and when in time, such as what event was he addressing?

Answer 1

Robert F Kennedy asked, "If not us, who? If not now, when?".

Answer 2

I think it was a reference to the fall of Communism; he realized it wasn't working and he was talking about how he had the courage to change at the time (late 1980s).