Vardy scored a brace in a friendly win over Burton Albion on Tuesday while Kramaric has already been on the scoresheet for the Foxes this pre-season.
Ranieri told Foxes Player: "I think it's important for strikers to score goals. Vardy has scored, Kramaric has scored and slowly, slowly I think the other strikers will score as well.
"I'm very impressed because the tempo is very high. Today we played 90 minutes, which is important and we must now focus for Sunderland now."
Leicester kickstart the 2015/16 Premier League season against the Black Cats on August 8.