A US military prosecutor on Thursday accused Bradley Manning of betraying his country and uniform by leaking secret files, urging a judge to find him guilty of "aiding the enemy."

In closing arguments in Manning's espionage trial, Major Ashden Fein painted him as a reckless, selfish turncoat who knew America's foes would see the trove of classified reports he gave to anti-secrecy website WikiLeaks.

Fein told the court that Manning "delivered these documents ready-made for use by the enemy."

As an army intelligence analyst, Manning had pledged under oath to safeguard sensitive information held by the government then "abused and destroyed this trust," Fein said.

"The flag meant nothing to him," he alleged.

The 25-year-old Manning has already admitted to leaking hundreds of thousands of classified documents to WikiLeaks.

But he has denied other charges against him, including the most serious count that he knowingly "aided the enemy."

That charge carries a possible life sentence, and a guilty verdict could break new legal ground for future leak cases.

Displaying a photo of Manning smiling and looking "gleeful" -- allegedly after he began his document dump to WikiLeaks -- Fein said evidence in the court-martial showed Manning had the intention of wreaking havoc.

Manning "wasn't interested in oaths," Fein said. "He was interested in making a name for himself."

Working in military intelligence in Iraq, Manning had been trained to know that "terrorists" use the Internet to gather information to help in preparing attacks against the United States, he said.

Citing an instruction session that Manning himself had presented to fellow soldiers, the private listed foreign governments, terrorists and hackers as among potential adversaries seeking US secrets, Fein said.

Manning was also aware that WikiLeaks had been identified in three military intelligence reports as a possible threat to national security, as the site sought to expose any classified material, according to Fein.

The prosecution depicted Manning as agent for "information anarchists" at WikiLeaks after having corresponded with founder Julian Assange and others in the organization.

From November to December 2009, Manning was "searching for topics related to one mission -- finding and disclosing what WikiLeaks wanted," Fein said.

The defense was due to offer its closing argument later Thursday.

Three years after Manning's arrest in Iraq over what officials at the time called the biggest national security leak in America's history, this will be their last opportunity to make their case before the judge, Colonel Denise Lind, delivers a verdict.

Born in Oklahoma to an American father and a Welsh mother, the slight, bespectacled Manning has portrayed himself as a truth teller who leaked a cache of diplomatic cables and military intelligence reports to shed light on US foreign policy excesses.

Manning has told the court he believed the reports he saw in his job "needed to be shared with the world" and it "would help document the true cost of the wars in Iraq and Afghanistan."

Manning has pleaded guilty to ten lesser chargers of federal espionage, computer fraud and wrongful storage of classified information, which could carry a sentence of up to 20 years in prison.

Prosecutors are trying to prove 12 additional counts, including theft of US property, exceeding authorized access on a government computer and the "aiding the enemy" charge.

Even if he is acquitted of aiding the enemy, Manning faces a possible sentence of 154 years behind bars.

The court-martial has taken on added importance in the wake of revelations from another young man working with classified information, Edward Snowden, a former intelligence contractor who recently blew the lid on US surveillance of phone records and Internet traffic.

The outcome of Manning's trial could have implications for the case against Snowden, if he is ever extradited to the United States after having fled to Moscow via Hong Kong.

Rights groups have criticized US authorities for the level of secrecy surrounding the Manning trial and reporters covering the court-martial at Fort Meade, Maryland, northeast of Washington, were subjected to elaborate security measures Thursday.

In a room where the proceedings were transmitted by video link, armed military police patrolled to ensure no journalist tried to tweet or surf the Internet while the court was in session. Reporters are allowed to file from the room only during breaks.