President Moise was assassinated when gunmen stormed his home on 7 July.
Prosecutor Bedford Claude said that Mr Henry had multiple phone calls with suspect Joseph Felix Badio just hours after the assassination.
Mr Claude said Mr Henry was being "invited" to attend, as he did not have the authority to officially summon him.
Haiti's head prosecutor has invited Prime Minister Ariel Henry to explain his connection to the main suspect in the killing of President Jovenel Moise.