Fury said on Friday a contract had been sent to Joshua for a Wembley Stadium showdown.
Hearn begged to differ.
"We have been sent no contract for a fight in September," he said to IFL TV, but he added there were talks with Fury's team.
He said Joshua's team were also negotiating a fight with former heavyweight champion Deontay Wilder in December and would not alter those plans.
"If our plans don't come to fruition we would of course be open to discussing a fight with Tyson Fury," Heard said.
"The Tyson Fury fight is a fight Anthony Joshua wants."
Fury has not fought since retaining his title with a 10th-round stoppage of fellow Briton Derek Chisora in December.
Fury has 33 wins and a draw from 34 bouts, while Joshua has 25 wins and three losses in his 28 professional fights.
