The Grove based principal said the format, not producing a pole sitter until the morning of grand prix Sunday, must change, 'and urgently.'
He also told Italian magazine Autosprint: "There might be ... small modifications in the future.
"The big problem is that some cars have smaller (fuel) tanks than others."
Williams admitted the possibility of reinstating the classic 12-lap, one-hour system, but outlined a hitch in integrating it with the new one-engine per two races rule.
He said: "At least, with the current system, it's all over in one lap."