a bridge too far
Definition from Wiktionary, the free dictionary
In reference to Operation Market Garden, Allied airborne military operation of 1944.
- (idiomatic) A step or action that is too ambitious; an act of overreaching.
2006, Adair Broughton, Crossing the Bridge of Infinity, page 40:
- Cloning was an interesting concept. Cloning body parts was again just man's search for immortality riding on the back of naive altruistic medicinal benevolence. But cloning a person was a bridge too far.