South African Van Niekerk, who electrified last year's Rio Olympics by smashing the 400 metres world record with a time of 43.03 seconds in the final, had set his sights on a double gold in London.
The 24-year-old's hopes, however, looked like being scuppered by the schedule, which originally put the 400 final on August 8, just hours after the first round of the shorter sprint.
The IAAF, world athletics' governing body, has sought to avoid the clash by moving the first round of the 200m to August 7 to "better allow for a 200m/400m doubling opportunity".
It said in a statement it had responded to requests from athletics federations, including South Africa's.
“I am also delighted that the Council today approved the 200m and 400m double. These double headers create great excitement among both athletes and fans,” IAAF President Sebastian Coe said.
The world championships run from August 4-13.
Read the original article on Eurosport: Van Niekerk's world championships double bid boosted by schedule change