“It was planned to prevent further bloodshed, it was a defensive action,” RIA Novosti quoted him as saying.
According to the adviser, US President Donald Trump acted in accordance with his authority, ordering an operation against an Iranian general.
He noted that the United States expects Iran to choose the “right path” for negotiations, rather than escalating the conflict.
O'Brien added that closed briefings on the situation around Iran will be held in Congress next week.
On the night of January 3, Baghdad, the General of the Islamic Revolutionary Guard Corps, Kassem Suleimani, was killed. The Pentagon has confirmed that the operation, which killed a high-ranking Iranian military, was personally sanctioned by Donald Trump.