SEATTLE: The U.S. soldier accused of killing 16 Afghan civilians during nighttime raids on two villages last year deferred entering a plea Thursday to charges that could bring the death penalty. The judge ordered a review of his sanity before he can present any mental health defense.

Staff Sgt. Robert Bales faces 16 counts of premeditated murder and other charges in the attack, which caused such outrage that the U.S. temporarily halted combat operations in Afghanistan.

Defense lawyer John Henry Browne told The Associated Press earlier this week that Bales would plead not guilty, but another attorney, Emma Scanlan, told the judge that Bales would defer entering a plea.

Prosecutors say Bales had been drinking early last March before slipping away from his remote outpost in southern Afghanistan to attack the villages. Nine children were among the dead.

Lawyers for Bales argue that he was on his fourth military deployment and may have been suffering from a traumatic brain injury when he was knocked out by an improvised bomb explosion during one of his tours in Iraq. They have criticized the base at Camp Belambay where Bales was stationed, saying that Special Forces members there gave him banned substances including alcohol, Valium and steroids.

The lawyers insist that by seeking the death penalty against Bales, the Army is ignoring its own responsibility for sending him to war.

The judge, Col. Jeffrey Nance, said Thursday he will order that Bales undergo an official review of his mental health, called a "sanity board," after prosecutors argued that without doing so, Bales should be barred from presenting any sort of mental health defense.

Such reviews are conducted by neutral doctors tasked with discerning a defendant's mental state at the time of the crime and whether he's competent to stand trial. Bales' mental health has been expected to be a key part of the case.

Bales' attorneys have thus far refused to let him take part in the sanity board because the Army would not let him have a lawyer present for the examination, would not record the examination and would not appoint a neuropsychologist expert in traumatic brain injuries to the board.

However, in a reply to the government's motion, Scanlan wrote Tuesday that Bales will participate - as long as only certain information about the results are forwarded to prosecutors. Prosecutors should promptly receive findings about his current competence, but nothing about his mental state at the time of the attack, she wrote.

That information should not be turned over to the government until Bales' defense team actually gives notice of their intent to use a mental health defense or to have an expert testify, Scanlan said.

The judge said the conditions of the sanity board could be worked out later, but the review will be held.

Prosecutors also argued Thursday to set the trial quickly - for June 10 - because many witnesses remain in a volatile part of Afghanistan. Two possible witnesses have already been killed in separate and unrelated attacks, they noted, and as U.S, troops withdraw, access to those witnesses will get tougher and more dangerous.

"Simply stated, with each day that passes, the government's right to a fair trial is further jeopardized," they wrote in court filings.

Scanlan called that unrealistic, given how much time the defense team needs to review more than 30,000 pages of materials and find and interview witnesses. The defense has suggested a May 2014 trial date.

Scanlan noted that Bales' case was formally referred to a court martial just last month. For the last five U.S. courts martial where the death penalty was a possible punishment, the average elapsed time from date of referral to date of trial was one year and eight months, she wrote. Setting Bales' trial for this June would be a record pace, she suggested, and would risk harming the quality of his legal defense.