The Liverpool manager had previously said that England international Downing was not intended on being sold, but he was 'offered a really good deal at West Ham'.
"He wasn't one we were pushing out of the door. After the early part of last season, he became a very valuable member of the squad," the Northern Irishman told the Liverpool Echo.
"But he gets the chance to go to West Ham, picks up a long-term deal, plays week in, week out and at this stage of his career that's obviously what he wanted."
However Downing says that it was Liverpool who orchestrated the move, and not him.
"They said they wanted to keep me but they accepted a fee," said the winger to The Sun.
"I don't know about 'an incredible deal' - I got a four-year contract.
"I'm disappointed that one minute I was staying, the next I was gone."