Details about the characters the trio will play if they really sign the deal are not yet out, reported Aceshowbiz.
If Hardy, 38, gives his nod to the project this will be his third film with the 45-year-old filmmaker.
The duo have previously worked together in "Inception" and "The Dark Knight Rises".
"Dunkirk" is inspired by Operation Dynamo, the miraculous evacuation of the British Expeditionary Force (BEF) and other Allied soldiers from the beaches and harbour of Dunkirk, France.