Can't use TComponent in thread object?

I've added a Thread Object named TProgressThread to my Delphi7 Win32
project. I created this method in the unit:

procedure TProgressThread.GetRemoteFile;
begin
FtpClient1 := TFtpClient.Create(Self);
....
end;

I get this error when compiling:

[Error] ProgressThread.pas(72): Incompatible types: 'TComponent' and
'TProgressThread'

Line 72 is the FtpClient1 line above. I'm trying to put the
downloading of a file on its own thread. Why can't I use the
FtpClient1 object in the thread class?

Thanks,
Brett

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