The two singers have been getting close in recent months, showering each other with compliments on social media, but both have been keen to point out they are just good friends.
And now Mayer has invited the "Bad at Love" singer to join him on his "Current Mood" Instagram Live show to address the romance reports that won't go away.
"The fact that we're both alpha types, while not prohibitive, would make a romantic relationship difficult, especially when compounded by the fact that we're both highly driven and creative artists who value our independence," Mayer said.
"For being my not-boyfriend, you really do know me so well," Halsey added.
She previously addressed the rumours after sharing a video of herself and John FaceTiming on her Instagram Stories with the caption, "7am carpool karaoke with John Mayer."
She wrote: "Just had a groundbreaking idea. What if...we let female artists...have friends...without assuming that they are sleeping together (sic)? I know it's, like, completely ambitious but like, imagine if we like, tried?".