WASHINGTON — The Army psychiatrist accused of the Fort Hood massacre apparently acted alone and without outside direction in the attack, investigative officials said Monday evening.

Maj. Nidal Malik Hasan will be charged by the U.S. military rather than in a civilian court, they said.

Hasan communicated 10 to

20 times with a radical imam overseas who in the past came under scrutiny for possible links to terror groups, the investigative officials and a U.S. official disclosed. The investigative officials said the communications began last year and continued into this year and “were consistent with the subject matter of his research.” The U.S. official said the communications were with the imam, Anwar al-Awlaki.

U.S. officials were aware of the communications since last year, but no formal investigation was ever opened based on them, the officials said.

The officials spoke Monday evening on condition of anonymity because they were not authorized to discuss the investigation on the record. Awlaki, who was released from a jail in Yemen last year, writes a blog that denounces U.S. policies as anti-Muslim.

Investigators tried to interview Hasan on Sunday at the military hospital where he is held under guard, but he refused to answer and requested an attorney, the officials said.

In Killeen, Texas, near Fort Hood, Hasan’s attorney expressed doubt that his client could get a fair trial. Hasan remains under guard at a military hospital but began talking to doctors there on Monday.

Retired Col. John P. Galligan, a defense attorney retained by Hasan’s family on Monday, said he did not know whether Hasan had been medically cleared to be interviewed, but he asked investigators not to speak to his client.

“There’s a lot of facts that still need to be developed, and the time for that will come in due course,” Galligan said.

Hasan, 39, is accused of opening fire at the Army post on Thursday, killing 13 people and wounding 29 before civilian police shot him in the torso.

Hasan was awake and talking on Monday, said Dewey Mitchell, a spokesman for Brooke Army Medical Center.

Investigators are trying to establish a motive in the shootings. But details that have emerged indicate Hasan was an observant Muslim who was strongly opposed to the wars in Iraq and Afghanistan and appeared to be struggling to reconcile his faith and his duty as a military officer. His family said he was going to be sent to Afghanistan in November and was trying to get out of the assignment.

Galligan questioned whether Hasan could get a fair trial, particularly given President Barack Obama’s planned visit to the base today for a memorial service.

“You’ve got his commander in chief showing up tomorrow,” Galligan said. “That same kind of publicity naturally creates an issue as to whether you find a fair and impartial forum, whether that’s in the military or even if it were in a federal forum.”

Meanwhile, Awlaki, a radical American imam who had contact with two of the Sept. 11 hijackers and was a spiritual leader at a Virginia mosque where Hasan was said to have worshipped occasionally, praised the U.S. soldier on his personal Web site Monday.

“Nidal Hassan is a hero,” wrote Awlaki, who lives in Yemen.

“He is a man of conscience who could not bear living the contradiction of being a Muslim and serving in an army that is fighting against his own people.”

In December, Awlaki, on his Web site, encouraged Muslims across the world to kill U.S. troops in Iraq.

Awlaki left the United States in 2002, eventually traveling to Yemen. His whereabouts have been unknown since he was released from a Yemeni jail last year. He is on Yemen’s most-wanted militant list, according to three Yemeni security officials.

The officials said Awlaki was arrested in 2006 with a small group of suspected al-Qaida militants.

They said he was released more than a year later after signing a pledge not to break the law or leave the country. The officials spoke on condition of anonymity because of the sensitivity of the issue.