Nasser al-Khater, talking to journalists in Doha, said at the moment the country was continuing to prepare for a 32-team tournament in three years' time.
"No decision will be made without the agreement of Qatar, this is an important point," he said. "It will be a joint decision."
He added: "We are waiting for the results of the feasibility study, and once they are ready, (FIFA) will share them with us... to see if it is possible".
FIFA is carrying out the study into increasing the number of teams by 16 in 2022 and will announce a final decision in March.
Last month FIFA president Gianni Infantino said in Doha that a "majority" of football federations supported the increase.
Any decision to extend the tournament would though be faced by huge logistical and political problems.
The Qatar World Cup, the first in the Middle East, will take place over 28 days in November and December 2022, not the usual 32.
Officials have said previously that is not possible for Qatar to change the number of days, so one option would be to host tournament games across the region with neighbouring states.
But that is complicated by Qatar being at the centre of the worst diplomatic crisis to hit the Gulf in years.
Since June 2017, it has been politically and economically isolated in a rancorous diplomatic dispute with former allies, including Saudi Arabia, United Arab Emirates and Bahrain.
A 48-team World Cup is set to become the norm from 2026, when the World Cup will take place in the USA, Mexico and Canada.