ATP chairman Andrea Gaudenzi said there were "50 calendar options" for this year, but admits tennis could be one of the last sports to resume.
The ATP and WTA Tours have been suspended through July 13 amid the coronavirus pandemic.
While Wimbledon was cancelled, the French Open was pushed back until September amid uncertainty over when, and if, play will get underway in 2020.
Gaudenzi said tennis may have to wait longer than other sports to resume due to the amount of travel.
"We have 3,000-4,000 people coming from all over the world and therefore tennis could be one of the last sports to return," he told Sky Sport on Friday.
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"We have 50 calendar options. Nothing is yet decided. We will make decisions late May.
"There are assumptions [like] playing on the red clay after the US Open if all goes well and then continue with the normal season – in Asia, indoors and close with the [ATP] Finals in London."
There have been more than 1.6 million cases of coronavirus worldwide, with the death toll exceeding 102,000.
