A military jury has sentenced Major Nidal Hasan to death for killing 13 people during the 2009 shooting rampage at Fort Hood.

Hasan, 42, never denied being the gunman and has said the attack on unarmed soldiers was motivated by a desire to protect Muslim fighters in Iraq and Afghanistan.

Because he did not dispute the allegations, the trial has been primarily a pursuit of the death penalty.

The same jury that sentenced him to death on Wednesday also found him guilty last week of the attack, which also wounded more than 30 people at the Texas military base.

Before an execution date is set, the sentence will face years, if not decades, of appeals.

This is his debt to society. This is the cost of his murderous rampage. Col. Mike Mulligan, lead prosecutor

Earlier on Wednesday, a prosecutor told jurors that it would be "wrong and unsupportive" to tie Hasan's actions to a wider cause.

"He will not now and he will never be a martyr. He is a criminal. He is a cold-blooded murderer," said the lead prosecutor, Colonel Mike Mulligan. "This is not his gift to God. This is his debt to society. This is the cost of his murderous rampage."

A few minutes after Mulligan finished, Hasan said he would give no closing argument, passing on his final chance to address jurors before they began deliberating his fate.

Hasan's choice marked a continuation of an absent defence strategy that he has used since his trial began three weeks ago.

At the start of his trial he gave a brief opening statement, during which he said evidence would show he was the shooter and described himself as a soldier who had "switched sides."

But he called no witnesses and did not testify, and he questioned only three of the nearly 90 witnesses called by prosecutors before he was convicted.

Hasan becomes the sixth man on death row at the US military's prison at Fort Leavenworth, Kansas.

A military execution would require the approval of the Fort Hood commanding general and the US president in order to take place.

The US military last executed a prisoner in 1961.