The Reds have made seven acquisitions, and Mourinho believes they will be title contenders this season.
Mourinho said: "The top five are the top five. In the end the top five have that bit more responsibility.
"History plays a part and investment another."
Liverpool are reportedly hoping to beat Arsenal to Real Madrid winger Denis Cheryshev.
Spanish paper AS recently claimed Arsenal were considering making a £15million bid for the 24-year-old.
GETTY
Liverpool are hoping to sign Denis Cheryshev (left)
But fresh reports in Spain suggest Liverpool are optimistic they will have a £14.8m offer accepted.
Alberto Moreno could leave Liverpool this summer, according to reports.
Jose Mourinho Manager Profile
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Barcelona and Roma have both been credited with an interest.
And Moreno even came under fire with club legend Mark Lawrenson, who told the Liverpool Echo that the left-back had behaved like a 'little boy' at times last season.