Australia Chief of the Defence Force Angus Campbell on Tuesday described the possible intelligence leak by the United States a “serious” incident and said that the U.S. was engaging with its partners to understand the consequences.

“The issue of maintaining security of information is critical to the development of national capability and to the trust and confidence across allies and partners,” Campbell said in response to questions after a speech at the Lowy Institute.

U.S. national security agencies are reviewing how they share their most sensitive secrets inside the U.S. government, and dealing with the diplomatic fallout from the release of dozens of confidential documents, three U.S. officials said.