"I am proud of the progress he has made. When we brought him here people were talking - especially because he didn't score for 14 games or something like that," the Liverpool boss told the club's official website.
"But he showed his quality; showed he was a good player and a fantastic professional. He is a nice person. We know we will miss him but you can't stop a player who wants to play every week.
"He understands that with Torres here and Gerrard as a second striker, like he was at the end of last season, it will be difficult for him.
"Everything is friendly. I've talked to him and the agents. If he can agree with Portsmouth it will be perfect for everyone.
"People need to understand that we have supported Peter from the day he signed and we offered him a new contract [before the summer]. But I can understand that he wants to play every week, wants to start every game.
"As a manager you have to understand these situations. Also, a few people in the press were talking about £7million - so then I talked about £15million because I wanted to protect the club. But I know you need to respect the players.
"So, we have now more or less agreed a transfer fee and now it's just the player talking to Portsmouth and finding a solution."
