The first witness today at Manning's sentencing hearing was former Deputy Assistant Secretary of State Elizabeth Dibble.
She says agency officials reacted with "horror and disbelief" when WikiLeaks began publishing the leaked cables in the fall of 2010.
The former Army intelligence analyst faces up to 136 years in prison for sending the cables and more than 4,70,000 Iraq and Afghanistan battlefield reports to the anti-secrecy website.
The government opened its sentencing case yesterday with testimony that WikiLeaks' publication of the leaked battlefield reports fractured US military relationships with foreign governments and silenced some friendly Afghan villagers.