How to stop IdHTTP GET and POST?

I have a Thread to run GET/POST of a TIdHTTP. I use thread because I don't want GET/POST to blocking main thread.
But how to stop the GET/POST from main Thread? I tried to disconnect the IdHTTP in main thread, but exception box appear.

Here is the Thread I implemented for HTTP GET and POST:

Type
  THttpAction = (haGet, haPost);
  THTTPActionThread = class(TThread)
  private
    _Action:THttpAction;
    _HTTP:TIdHTTP;
    _URL:String;
    _Stream:TStream;
  protected
    procedure Execute; override;
  public
    constructor Create(AAction:THttpAction; AHTTP:TIdHTTP; const AURL:String; AStream:TStream);
  end;

{ THTTPActionThread }

constructor THTTPActionThread.Create(AAction: THttpAction; AHTTP: TIdHTTP;
  const AURL: String; AStream: TStream);
begin
  _Action:=AAction;
  _HTTP:=AHTTP;
  _URL:=AURL;
  _Stream:=AStream;

  FreeOnTerminate:= True;
  Inherited Create(False);
end;

procedure THTTPActionThread.Execute;
begin
  If Assigned(_HTTP) and Assigned(_Stream) then
  try
  try
    Case _Action of
      haGet: _HTTP.Get(_URL, _Stream);
      haPost: _HTTP.Post(_URL, _Stream);
    End;
  finally
    _Stream.Free;
  end;
  except
  end;
end;

//Thanks!
--
Samson Fu