Three State Department employees are due to testify at a preliminary hearing Thursday for US soldier Bradley Manning, who faces a court-martial for allegedly leaking hundreds of thousands of classified documents.

The employees, whose names and titles were not released, will be asked to provide "State Department evidence" during the hearing underway at an army base in Fort Meade, Maryland, according to a military official who spoke on condition of anonymity.

They are to testify about the government's "damage assessment" following the publication of a trove of US documents Manning is accused of leaking to whistleblower website WikiLeaks.

Defense lawyers are presenting their case for dropping 10 of 22 charges against Manning during three days of preliminary hearings due to end Friday.

The junior intelligence analyst, whose trial is scheduled to begin on September 21, could be jailed for life if convicted of "aiding the enemy" -- one of the criminal charges that judge Colonel Denise Lind has let stand. He has yet to enter a plea.

Manning is accused of giving WikiLeaks hundreds of thousands of military and classified government documents, which the website then posted online, leaving US officials red-faced and scrambling to staunch the ensuing diplomatic firestorm.

US officials say the massive leak put national security at risk, although no damage assessment has yet been made public.

On Wednesday, the judge ruled that Manning's legal team should be given access to government documents on the scandal, handing the defense a partial victory.

Lind ordered the government to hand over a redacted version of a report by the Pentagon's Defense Intelligence Agency evaluating the impact of Manning's alleged actions.

[Photo via AFP]