The Bundesliga outfit trounced Rot-Weiss Essen 5-1 on Sunday, with all five of their goals coming inside the opening half-hour.
Dortmund's victory means they remain unbeaten in pre-season and head coach Klopp is encouraged by the team's progress.
However, with Mats Hummels and Erik Durm yet to return following Germany's successful World Cup campaign and Marco Reus still absent with ankle ligament damage, Klopp concedes he would prefer to have more players at his disposal.
"We just keep working. I see a lot of things I want to see, but sometimes it's the opposite," said the 47-year-old. "But that's okay because I know why - it's no problem.
"For the moment, we are working really hard with all the players we have.
"In the next friendly, we will have Adrian Ramos and Sokratis Papastathopoulos will be back as well. It's step-by-step. In three weeks, the league starts - and on that day we hopefully have 15, 16 men who are able to play.
"And one week later we should have a few more options. Obviously I would love to have all my players back and together now.
"It would be great to work seven weeks with your whole squad. Some were at the World Cup, some were injured at home - it will take a while to get them all back into our team."
