Witness at Manning sentencing testifies about information-sharing restrictions to support prosecution

FORT MEADE, Maryland (Reuters) - Washington had to restrict access to an intelligence-sharing system after the biggest leak of classified information in U.S. history, a former official said on Friday at the sentencing hearing of Bradley Manning, the soldier convicted of the leaks.

Tightening access to the system undid the very benefits the system was meant to provide, according to Susan Swart, a former U.S. State Department official who was responsible for the movement of diplomatic cables when they were leaked and published by the anti-secrecy website WikiLeaks in 2010.

But under questioning from Manning's lawyer Swart reluctantly acknowledged that after access to the information-sharing system was restricted, officials could still use it "technically speaking." She was quick to add "but I don't buy the logic."

The information-sharing system was put in place in 2006 to address intelligence failures exposed by the September 11, 2001 attacks.

A military judge on Tuesday convicted U.S. Army Private First Class Manning, 25, of criminal charges including espionage and theft of classified information from the intelligence system, known as Net-Centric Diplomacy. The former military intelligence analyst was acquitted of the most serious charge of aiding the enemy, sparing him a life sentence without parole.

The sentencing phase of the court-martial at Fort Meade, Maryland began on Wednesday and was expected to last at least until August 9, military officials said. The military prosecutors were first to call their witnesses and will be followed by defense witnesses.

The convictions carry a maximum possible sentence of 136 years, and prosecutors are seeking to establish the damage caused by the leaks.

Swart, who left her job in 2012, said she felt the system was secured by vetting users before allowing them to view classified information. She said it was "not very feasible" to require the large number of users to have passwords.

As Manning's lawyer was exploring the reaction of her superiors to the breach, she said: "I don't feel blamed."

Access to classified information remains a sensitive subject after Edward Snowden, a U.S. intelligence contractor, revealed the National Security Agency's secret program to collect phone and Internet records.

Snowden was granted temporary asylum in Russia on Thursday. U.S. authorities want Snowden to return to the United States to face charges of espionage.

Manning's lawyers, who had portrayed him as naive but well intentioned, were expected to ask Judge Colonel Denise Lind for leniency in sentencing. They argued that the soldier's aim had been to provoke a broader debate on U.S. military policy, not to harm anyone.

Prosecutors had said Manning hurt national security and damaged relationships with intelligence sources overseas.

Manning was serving in Iraq in 2010 when he was arrested and charged with leaking files, including videos of a 2007 attack by a U.S. helicopter gunship in Baghdad that killed a dozen people, including two Reuters news staff. Other files contained diplomatic cables and secret details on prisoners held at Guantanamo Bay.

(By Tom Hals. Editing by Barbara Goldberg and Grant McCool)