By Tom Ramstack

FORT MEADE, Maryland (Reuters) - Bradley Manning, the U.S. soldier convicted for giving classified documents to the WikiLeaks website, exhibited behavior that could have served as a warning he was unsuitable to serve abroad as an intelligence analyst, his lawyer said in court on Monday.

As the defense began its case in the sentencing phase of Manning's court-martial at Fort Meade, Maryland, lawyers discussed a psychological assessment report that describes him as having "regressed stages of development" and "narcissistic personality traits."

Manning's lawyer David Coombs said the report was important to explain the motivation for the unauthorized release of more than 700,000 diplomatic and military documents and videos, the biggest leak of classified information in U.S. history.

"It's mostly to explain to the court what was going on," Coombs said. Coombs has said Manning will make a statement during sentencing.

The court heard how Manning had been referred for counseling in December 2009 and during a session, he flipped a table and in another outburst, tried to grab a gun but was restrained by another soldier.

Manning, 25, of Crescent, Oklahoma, was convicted on July 30 of 20 counts, including espionage and theft. He was found not guilty of the most serious count of aiding the enemy, which carried a sentence of life without parole.

Manning could face up to 90 years in prison and his lawyers are scheduled to present a dozen witnesses as they argue for a lenient sentence from Judge Colonel Denise Lind. The defense is likely to conclude its case this week.

Throughout the trial, defense lawyers have portrayed Manning, who is gay, as naive but well-intentioned and struggling with his sexual identity when he arrived in Iraq in November 2009. They contend he was conflicted by his exposure to war and a trove of military data.

The defense tried to show on Monday that Army commanders failed to notice personality traits that might have made Manning unfit to serve as an intelligence analyst in Iraq, where he released secret files to anti-secrecy website WikiLeaks in 2010.

Prosecutors objected, saying the defense should not be allowed to use the report because they were not given prior notice. The judge said she would rule on the report's admissibility as soon as Monday.

Coombs questioned Manning's brigade commander, Colonel David Miller, about whether mid-level officers failed to respond properly to behavior by Manning showing he should not be placed in an intelligence analyst position.

Manning was referred to counseling in December 2009, Miller testified. Miller said he was not told about Manning's behavior until after the leaks were published.

"In context, a soldier flipping a table is not something that would rise to the level of a brigade commander," he said.

The prosecution presented its last witnesses on Friday and had tried to show damage that Manning's leaks had done to the United States.

In setting Manning's sentence Lind is determining how much damage he did. She gave a boost to the defense by disallowing evidence that failed to show a direct impact from Manning's leaks.

Lind ruled in preliminary hearings that the sentence would be trimmed by 112 days because Manning was mistreated following his 2010 arrest in Iraq.

Manning's case has drawn support from activists who contend he should be commended for revealing details about U.S. actions overseas. A U.S. rights group, RootsAction, has collected more than 100,000 signatures urging the Norwegian Nobel committee to give this year's Peace Prize to Manning.

(Editing by Ian Simpson and Grant McCool)