Liverpool have only signed Mohamed Salah from Roma and Dominic Solanke, who was out of contract at Chelsea, so far this summer and have been frustrated in their efforts to sign RB Leipzig winger Naby Keita and a top-class centre-half following the Virgil van Dijk saga.

"Of course the transfer market opened a few days ago," the Liverpool manager told the club's official website.

"Yes, it will be a difficult one, maybe it's getting more and more difficult, especially in England but we have made a lot of good things so far. If you cannot see it so far, you can imagine we have done a lot of things behind the scenes.

"Sometimes you need to be patient and that's what we are in the moment -- to wait for the right moment and then we will see what happens."

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Meanwhile, Jon Flanagan is back at Liverpool for preseason training after spending last season on loan at Burnley.

Klopp sent the defender away from Anfield on loan in order to gain regular football following two long-term knee injuries, but he was restricted to just 10 appearances at Turf Moor.

"I've been doing work over the summer, trying to keep fit and ticking over," he told the club's official website. "We know it's going to be a tough preseason so it's vitally important for me to come back raring to go and in good shape.

"I can't wait to get started. I think it's a bit of a fresh start. I had a few injuries [but] hopefully they're past me now and hopefully I can kick on and show what I can do."