"'When?' Is the big question. And that's something that none of us really know the answer to at the moment," Tomlinson explained. "I feel like what's most important is when we do get back together, we're all on the same page and we all have done what we want to do individually."
He went on to add: "I think that's vitally important for when we get back. It's just 'when' as far as I'm concerned, but I don't know the answer to the question 'when' yet."
In 2016, the multiplatinum group announced they were going on hiatus. Since then, all the members, including Tomlinson, have released solo music. The 27-year-old has released tracks with Steve Aoki ("Just Hold On") and Bebe Rexha ("Back to You"); the first went gold in the U.S. and the second went platinum.
His most recent single, "Two of Us," is a stirring ballad dedicated to his mother, who died in 2016. However, that isn't the only tragedy that has befallen Tomlinson in recent years.
Last month, ET learned that the singer's 18-year-old sister, Félicité, was found dead, after which Tomlinson immediately canceled all promotional appearances over the next few weeks. His set at Free Radio Hits Live in Birmingham on Saturday was his first since her death.