Jürgen Klopp believes there is reason for "real optimism" ahead of the upcoming campaign after Liverpool returned to pre-season training on Wednesday.

The Reds joined back up at their Melwood training base with 22 members of the first-team squad - including new signing Dominic Solanke, returning loanees and Academy prospects.

While Liverpool's business for the summer transfer window is far from complete, the club still frustrated by their pursuit of Naby Keïta, Klopp is feeling positive after watching his players undergo fitness tests in mid-week.

The Reds season starts in six weeks, with pre-season beginning at Tranmere Rovers next Wednesday, with a Champions League qualifier soon to follow their Premier League opener.

Squad are all in good shape, says Klopp

Klopp hailed a "wonderful" and "absolutely deserved" rest period with Liverpool's squad having been off since mid-May, although others have been involved in international friendlies or tournaments.

The German told Liverpool's official website that he saw in the faces of his players that they are "ready to go" and admitted: "Of course, it's not what they love most. It's kind of a weird relationship. You don't want to do it [pre-season] but you know it's necessary, so you do. You feel bad before and you feel perfect afterwards."

Having completed several tests on the first day, Klopp insisted it is "important" for the club's staff to "know from which point we can pick them in the next few weeks" but said that the full squad "all look pretty much in a good shape."

Reds have kept in contact with internationals over the summer

Other members of the squad will return later in the summer having had international commitments, Emre Can having won the Confederations Cup with Germany in Russia last month.

But Klopp explained that he has kept in regular contact with all of his players, though revealed that he does not call them while they are on their holidays.

He added: "But when the training starts again and they have to do the [fitness] plan, then we are always in contact. They have to send me messages after they did their session."

Klopp said that he and his staff have "always" been "in contact" with those players who have played international football because it is "important how they feel before and after the game."

The manager insisted that it is "not really work" for him because he is "interested" in the shape of his players and said he has "had contact with all of them."

"We have a real reason for real optimism"

Liverpool's pre-season schedule takes them to Hong Kong, Germany and the Republic of Ireland - their journeys designed to ensure less miles are logged than last summer.

They face eight friendlies, starting with Tranmere next week and ending with a clash against Athletic Club in Dublin the final week before the Premier League season begins.

Klopp is hopeful that having carefully managed their pre-season programme, they can use it as a positive springboard for the start of the season proper at Watford on August 12.

He noted that "in a few weeks" they have "these [Champions League] qualifiers" and that "there will be pressure on the game" but reassured supporters that they "have the time to prepare [for] this."

"We have to use the basis we created last year. It was not too bad," the Reds boss continued. "We all know it could have been maybe a little bit better [than finishing fourth] but it could have been much worse."

Klopp declared that Liverpool are "now one of the top-four teams in England" and "want to keep this situation and work with it and improve."

He insisted: "The squad will be stronger this year than it was last year. That’s a real reason for real optimism."