Liverpool boss Jurgen Klopp has said that a move for Cristiano Ronaldo is "not business for the future" and bemoaned that there "must be different ways" to build a successful team.

Sources have told ESPN that Juventus forward Ronaldo is close to agreeing a deal with City, paving the way for a return to the Premier League for the first time since leaving Manchester United in 2009 in a then-world record £80 million transfer to Real Madrid.

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However, United manager Ole Gunnar Solskjaer hinted on Friday the club could be interested in bringing Ronaldo back to Old Trafford, saying "he knows that we're here."

With Ronaldo, 36, earning in excess of £500,000-a-week at Juventus, his arrival at either Manchester side would mean a huge increase in the club's wage bill for a player with little or no resale value.

And Klopp, who has spent just £36m on RB Leipzig defender Ibrahima Konate this summer, said he believes the prospective Ronaldo deal highlights the blueprint of some clubs being prepared to spend big for instant success rather than build over the long-term.

"I watched it [Ronaldo story] like a football supporter, but I have no knowledge about it," Klopp said in a news conference on Friday.

"It's not about me to judge that, but if other clubs can do it, it's not a business for the future, [the next] three to four years, it's about now and immediately.

"That's how some clubs are working and that's fine, but there must be different ways, clubs who look two or three years later and have success.

"It's not always with the best squad in the world, it's about developing as a squad and a club and that's what we have done.

"We have resources and have been building for a while. I have no time to look at other clubs. I see the news, but I have no time to think about what they can do.

"We brought in Konate. He wasn't a bargain, he cost money too. But all the offensive, attacking players other clubs are signing -- obviously they thought they needed it and they have the resources to do it, but we won't use it as an excuse."

This summer transfer window has seen some of the game's biggest stars move clubs, with Lionel Messi leaving Barcelona for Paris Saint-Germain, and sources have told ESPN that Madrid are edging closer to a deal for PSG striker Kylian Mbappe.

The commercial impact of those deals is huge for the parties involved, but Klopp says that he has yet to be asked to do a transfer for its commercial value to his club.

"I think with Messi and Ronaldo especially, there might be a commercial aspect of it, of course," Klopp said. "But I don't think PSG bought Messi for commercial reasons. Maybe yes, I don't know.

"They brought him in because Messi still has a lot to give for the football team and that's it. If Cristiano comes to the Premier League, that will be the first intention as well in that case.

"Nobody came to me for me to ever have to make a commercial signing, whatever that means.

"Nobody asked me about that and if that was to come, I would start thinking probably, but so far it never happened."