Mohamed Salah, Sadio Mane and Marko Grujic will travel with Liverpool for the club's pre-season tour of the United States of America, which begins next Saturday.
"We have to see how they present and then we'll see if they can play in the games".
He said: "That's the start for them".
"They had their holiday and then they'll come with us to the USA". They only had three weeks' holiday so it means they didn't lose too much. "They will be there".
Klopp also confirmed that striker Roberto Firmino, who reached the quarter-finals with Brazil, will report back for Liverpool's second training camp in France later in the month. "And then the last group [of World Cup players] comes much later".
England pair Jordan Henderson and Trent Alexander-Arnold, Belgium goalkeeper Simon Mignolet, and Croatia defender Dejan Lovren return a week later, giving them just seven days to prepare for the club's Premier League opener against West Ham on August 12.