The 29-year-old striker has not been called upon by his country since 2010 but has been told that he still has a chance of travelling to Brazil for the 2014 World Cup
The 29-year-old has been absent from the national team since 2010, with coach Joachim Low prolonging the three-year absence by opting against naming him in the squad to face Paraguay on Wednesday.
However, Bierhoff says the door remains open for Kiessling, who picked up the golden boot in the Bundesliga last season with 25 goals.
"It always hurts to see players making a name for themselves, but not really making the step into the national team," he told Sky.
"During my time, that was Martin Max. Joachim Low has said that all of the doors are open and it's up to the player to force his way in."
Kiessling, who is yet to score an international goal for his country, has earned six caps for Die Mannschaaft.