Ranieri's men have struggled to mount a convincing defence of their title so far, and are currently 13th in the standings after losing four of their eight Premier League matches and drawing another two.
They have, however, fared better in the Champions League, where they top Group G after two wins in two games, and Ranieri said he was prioritising success in Europe over the Premier League this season.
"At this moment this is the priority," the Italian, who started influential winger Riyad Mahrez on the bench during Saturday's 3-0 Premier League defeat by Chelsea, told reporters on Monday.
"In the Premier League, Leicester must be safe at the end of the year, the Champions League is now. In one month we play our Champions League -- in or out."
Ranieri denied his team were lacking fight and called on his players to give their best in their first-ever meeting with Copenhagen, who top the table in Denmark.
"Last season we were more compact and there was another style of football," Ranieri added. "Now everybody knows us and we try to change something.
"It is normal when you first play in Europe that the team loses something. They are human, not machines.
"We will have to give the best performance of the season, it is very important for us to get three points. We have to be strong, playing with passion, with heart, with the support of our fans. It will be a hard match until the end."
Leicester's Danish goalkeeper Kasper Schmeichel said he was relishing the chance to test his skills against a team from his homeland.
"Copenhagen are a team who are the top dogs in Denmark," Schmeichel, who has spent his whole career in Britain, said.
"It will be a special experience for myself to play against them, I've never played against a Danish team or a club game in Denmark."
Copenhagen are second in Group G and trail Leicester by two points, with a win and a draw in their first two matches.
(Reporting by Simon Jennings in Bengaluru; Editing by Rex Gowar)
