Lallana limped off after just 23 minutes of his side's 2-1 victory over Swansea City this afternoon having picked up a groin injury.
Klopp is unsure exactly how long the midfielder will be out of action for, but is hopeful of having him back available after the international break.
"Felt it, tried again, didn't work,. In this moment, he has no chance for the national team but hopefully 15 or 16 days should be enough to bring him back on the pitch (for Liverpool)," he told reporters.
"There was no sign of it in the week. These things can happen."
Lallana scored England's winner against Slovakia last month for what proved to be the team's only goal of the short-lived Sam Allardyce era.