Manning was arrested in Iraq in May 2010 on suspicion that he was the source of the huge database of US embassy cables that was passed without permission to WikiLeaks. He has spent the past 18 months in confinement, much of it in the early stages in conditions that some say were tantamount to torture.
Ahead of the Article 32, the army has released details of the precise charges against Manning. The most serious count is "aiding the enemy" - a charge that technically carries the death penalty though prosecutors have indicated they will not press for that.
In addition, Manning is accused of 16 counts of wrongfully causing intelligence to be published on the internet knowing that it is accessible to the enemy; five counts of theft of public property or records, eight of transmitting defence information, two of fraud in connection with computers and five of violating army information security.
If convicted of all charges, Manning would face a maximum sentence of confinement for life.
His support network plans to hold a rally outside the Article 32 at Fort Meade on the morning of the hearing, followed by a march the following day – Manning's 24th birthday.