Unable to find package ***. No packages exist with this id in source(s): "Local Nuget", Microsoft Visual Studio Offline Packages, nuget.org

I have to one library which I want to package and use in other projects. This library has reference to another project, that I do not want to publish as a package. To include it in the package I have added this lines in .cproj file:

<PropertyGroup>
<TargetsForTfmSpecificBuildOutput>$(TargetsForTfmSpecificBuildOutput);CopyProjectReferencesToPackage</TargetsForTfmSpecificBuildOutput>
      </PropertyGroup>

      <Target Name="CopyProjectReferencesToPackage" DependsOnTargets="ResolveReferences">
        <ItemGroup>
          <BuildOutputInPackage Include="@(ReferenceCopyLocalPaths-&gt;WithMetadataValue('ReferenceSourceTarget', 'ProjectReference'))" />
        </ItemGroup>
      </Target>

As a result I have both .dlls in packages lib folder, and this kind of nuspec file:

<?xml version="1.0" encoding="utf-8"?>
<package xmlns="http://schemas.microsoft.com/packaging/2013/05/nuspec.xsd">
  <metadata>
    <id>NugetSample</id>
    <version>1.0.1</version>
    <authors>NugetSample</authors>
    <owners>NugetSample</owners>
    <requireLicenseAcceptance>false</requireLicenseAcceptance>
    <description>Package Description</description>
    <dependencies>
      <group targetFramework=".NETCoreApp3.1">
        <dependency id="referenced project name" version="1.0.0" exclude="Build,Analyzers" />
      </group>
    </dependencies>
  </metadata>
</package>

But I get this error again:

Unable to find package referenced project name. No packages exist with this id in source(s): Local Nuget, Microsoft Visual Studio Offline Packages, nuget.org

It seems that visual studio tries to find this dependency as a nuget package again. How can I solve this problem?