The formal trial stage in the case of the WikiLeaks suspect Bradley Manning will begin on February 23, the US military has announced, when the soldier will be arraigned on all 22 counts relating to the largest leak of state secrets in American history.

Manning will be transferred on that day from his current imprisonment at Fort Leavenworth in Kansas to Fort Meade in Maryland, where he will be read all the charges against him and asked to give his plea. It will be the first occasion that he has come in front of a military judge representing the full power of the court martial system.

In most cases, the arraignment is a short and routine hearing that marks the accused's official bringing to trial. In Manning's case, however, it presents his trial lawyer David Coombs with the opportunity to raise objections to the conduct of the prosecution against his client.

In particular, Coombs has the option to complain about the exceptional length of time that Manning has been languishing in military jail. Under the US constitution, court martial cases must be brought within 120 days of charges being preferred against a suspect.

The military rule book, under rule 707 for speedy trial, makes clear that military justice must be dispensed quickly. It says that in some circumstances, delays may be prejudicial to the accused and may result in dismissal of the case.

A military spokesperson said that Manning's 120 days, known as his "speedy trial clock", began on 29 May 2010, yet he has continued to be held at the brig at Quantico marine base in Virginia and latterly at Fort Leavenworth for months beyond the deadline. The extra time taken to come to trial was due, the spokesperson said, to requests by Manning's own defence team and the period in which classified documents were being handled.

"Offenses ordinarily should be disposed of promptly to serve the interests of good order and discipline. Priority shall be given to persons in arrest or confinement."

Against that, the rule book allows for delays in exceptional circumstances, that can include a request by the defence for more time to prepare their case, delays relating to the mental capacity of the accused, and time needed to obtain security clearance for classified documents. Security clearance has been cited by the military authorities as an explanation for the delays that will see Manning spend almost two years in custody before his court martial begins.

The intelligence analyst was arrested in Iraq on May 26 2010 under suspicion of having leaked hundreds of thousands of secret documents and videos to the whistleblower website WikiLeaks.

It is not known whether Coombs intends to make the delayed proceedings an issue at the arraingment. But under the terms of the rule book, he has the right to lodge a motion to dismiss the case.

The burden would then fall on the military prosecutors to prove to the court that the delays were reasonable under army law.

Jeff Patterson, a leading member of the US branch of the Bradley Manning support network, said that the official opening of the trial stage would finally allow the defence to raise serious complaints about the process so far in front of a fully-designated military judge. "We hope that the real issues of this case – Manning's torture in Quantico, unlawful command influence, and the real and largely positive influence the documents had around the world – will now be properly addressed."

The alleged "unlawful command influence" refers to a comment by Barack Obama, commander in chief of the US military, who implied that Manning was guilty thus arguably prejudicing his fair trial.

Manning's charges include: aiding the enemy; wrongfully causing intelligence to be published on the internet knowing that it is accessible to the enemy; theft of public property or records; transmitting defense information; and fraud and related activity in connection with computers. If convicted he faces life in military custody.