The proposal states that in the third phase, the new ULEZ standards will be applied throughout London, UK, on buses, coaches and trucks from 26 October 2020 up to the North and South circular roads.
Standards for cars, vans and motorbikes will be applicable from 25 October 2021.
Khan said: “I am determined to take the bold action needed to protect the public from London’s poisonous, deadly air.
“I can’t ignore the shameful fact that London’s air is so toxic it harms children’s lungs, exacerbates chronic illness and contributes to thousands of premature deaths each year.”
Khan recently introduced a new weekday £10 Toxicity Charge (T-Charge) in central London for the oldest vehicles, along with the ongoing £11.50 Congestion Charge (C-Charge).
The second phase of the ULEZ will be introduced from 8 April 2019, 17 months ahead of the original plan.
It will replace the T-Charge and cover the same central area alongside and on top of the congestion charge throughout the day.
The daily charge for non-compliant vehicles will also be increased significantly.
Under the expanded range of ULEZ, approximately 100,000 cars, 35,000 vans and 3,000 lorries a day are expected to be affected.
Benefits of the expanded ULEZ will also include 43% fewer road kilometres, exceeding legal pollution limits in 2020 and 64% fewer in 2021.
NOx road transport emissions are also estimated to be reduced by 28% and 31% in outer and inner London respectively.