Gerets to join Al Hilal in summer
"The Al Hilal people wanted me to join in March. I told them it was just impossible. They agreed but kept the pressure on and in the end I made up my mind," the Belgian coach was quoted as saying by France Football on Friday.
Gerets, who announced he was leaving Marseille on April 29 when they were top of Ligue 1, said he had decided to quit the French club because of "a misunderstanding".
"We didn't meet early enough. I was ready to commit myself in the long term, I was expecting a signal; it never came," he told France Football.
Gerets admitted he was also joining the Riyadh club "because of the money". "I'm not a liar, the financial security they offered me counted," he said.
Gerets joined Marseille in September 2007 after the club had made a poor start to the Ligue 1 season.
They are now second, three points adrift of leader Girondins Bordeaux with two games to play.