Gpt-3.5-turbo API not returning correct amount of words

ChatGPT
1

When I send the following prompt to the gpt-3.5-turbo API:

{“role” : “user”, “content”: “Write me an essay of at least 1000 words on the 1996 american election.”}

I get an essay of 600-700 words. How can I force it to return 1000?