"We will hold conditional negotiations if the military leadership appoints its representative," according to a post from Khan's official X handle on Wednesday, which cited a message from him from inside a jail on Tuesday, Reuters reported.
The military's media wing did not immediately respond to request for comment
The army has previously ruled Pakistan for more than half of its 63-year history, but denies it is currently involved in politics.
Khan has been in jail since last August and was convicted in some cases ahead of a national election in February. He is also fighting dozens of other cases which are continuing.
Khan and his Pakistan Tehreek-e-Insaf (PTI) party say the charges were politically motivated to thwart his return to power.
Candidates backed by PTI had a stronger-than-expected showing in the country's election and a court recently ruled they were eligible for extra reserved seats, though still not enough to rule outright.
Khan said that one of the conditions for negotiations was that "clean and transparent" elections be held and that what he called "bogus" cases against his supporters be dropped.
He appointed Mahmood Khan Achakzai, a close political ally and leader in a smaller party, to represent him in talks.