Manning leaks caused diplomatic 'horror and disbelief': testimony FORT MEADE, Maryland (Reuters) - U.S. diplomats reacted with "horror and disbelief" when the anti-secrecy website WikiLeaks began publishing classified information in 2010, a U.S. State Department official testified on Thursday at the court-martial sentencing hearing for the soldier convicted of the leaks. Captain Angel Overgaard, a prosecutor whose questioning was apparently aimed at establishing how much damage the leaks caused, asked the official, Elizabeth Dibble, to describe the reaction to the exposure of hundreds of thousands of classified diplomatic and military documents and video. "Horror and disbelief that our diplomatic communications had been released and were available on public websites for the world to see," testified Dibble, principal deputy U.S. assistant secretary of State for Near Eastern Affairs. U.S. Army Private First Class Bradley Manning, 25, was convicted on Tuesday on criminal charges including espionage and theft, but was acquitted of the most serious charge of aiding the enemy, sparing him from a life sentence without parole. A military judge began hearing arguments on Wednesday in the sentencing phase of the trial in Fort Meade, Maryland over the biggest leak of classified information in U.S. history. The former military intelligence analyst's convictions carry a maximum possible sentence of 136 years. Prosecutors have said Manning hurt national security and damaged relationships with intelligence sources overseas. Manning's lawyers were expected to ask Judge Colonel Denise Lind for leniency in her sentence after portraying Manning as naive but well intentioned. They argued that the soldier wanted to provoke a broader debate on U.S. military policy, but not to harm anyone. Manning was 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. On Thursday, Manning's lawyer, Major Thomas Hurley, asked Dibble whether she always agreed that some of the government documents she reviewed should be classified. Dibble said she did not know of any problems with the U.S. government's system for classifying secret documents. At another point, Hurley quoted former U.S. Defense Secretary Robert Gates as saying governments in other countries knew the U.S. government "leaks like a sieve." Dibble replied, "I would say it makes a good sound bite, but I don't agree with it." She also testified that one of the foundations of diplomacy was establishing credibility, a time-consuming process that involves getting to know people and listening to their views. "There is an expectation of a certain degree of confidentiality so a person will not be burned," Dibble said. Observers said the guilty verdict could have "a chilling effect" on WikiLeaks by making potential sources in the United States more wary about handing over secret information. Writing by Barbara Goldberg; Editing by Grant McCool