I cannot create a truststore with a public key without a password

I am trying to create a truststore for the public key of a service that I want to consume, but it always asks me for a password for the public key file. This key is contained in a * .pem file and does not have a password. How do I create the truststore? I have tried not to provide the password but I get an error with the text "Can't build keys other: [Private key missing (bad password?)".
Thanks since now. Greetings.