© Mark Wilson/Getty Images fileArmy Pvt. Bradley Manning is escorted away from a hearing in February at Fort Meade, Md.
A military judge has rejected Pfc. Bradley Manning's attempt to have all charges against him dismissed and has ruled that he must face a court martial on charges that he leaked thousands of classified U.S. government cables to the anti-secrecy group WikiLeaks.

The court martial will start Sept. 21, military judge Col. Denise Lind said Wednesday.

Manning is accused of downloading more than 700,000 classified or confidential files from the military while serving in Iraq, the largest leak of classified documents in U.S. history.

Lind said that military prosecutors and Manning's defense team had decided on a tentative trial schedule beginning Sept. 21 and lasting through Oct. 12. The trial will start more than two years after Manning was arrested.

Defense attorney David Coombs had moved to dismiss all the charges because of what he called the prosecutor's intentional withholding of evidence needed to prepare Manning's defense. "The court finds no evidence of prosecutorial misconduct," Lind said in a pre-trial hearing.

Manning faces 22 charges on accusations that he downloaded files from the military's Secret Internet Protocol Router Network, or SIPRNet, while serving in the Army's 10th Mountain Division in Iraq.

One charge, of aiding the enemy, is a capital offense. The military court has said it would not seek the death penalty, but Manning could face life imprisonment if convicted.

Other charges against Manning include wrongfully causing intelligence to be published on the Internet and theft of public property.