Clyne, 26, has not played yet this season due to a back problem, but there was surprise on Monday when he was left out of Liverpool’s squad for the Champions League group phase.
In an update to fans on the club website, Klopp said the England international would miss the “majority” of Liverpool’s group games, which run from September 13 to December 6.
“Nathaniel is working hard on his rehab and we have kept a close eye on his progress, but the reality is we are looking at some time still before he is back and available for selection,” Klopp said.
“I am told it will be longer than just a couple of weeks, so we will continue to monitor and assess.
“It is pretty certain he’ll not be available for the majority of the Champions League group matches. If we are fortunate enough to still be in UEFA competition in the New Year, he could be added to the squad then.”
While Clyne’s absence is a blow, Klopp has drawn encouragement from the early-season displays of his young deputies Trent Alexander-Arnold and Joe Gomez.
“The medical guys are pleased with how he is responding and Nathaniel has shown a really strong attitude, given he is not someone who is used to being out injured,” Klopp said.
“What is positive for us is how Joe and Trent have stepped up and grasped their opportunities.”
Second in the table after the first three games of the Premier League season, Liverpool visit Manchester City on Saturday.
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