Washington  - The civilian and military heads of the US Air Force have tendered their resignations after two serious breaches of nuclear security in less than a year, Defence Secretary Robert Gates announced Thursday.

Air Force Secretary Michael Wynne and Chief of Staff Michael Moseley were both asked to leave after an internal investigation revealed that a "pattern of poor performance" and failure of leadership had led to two mishaps, Gates said.

The US in March said it mistakenly shipped fuses for detonating nuclear warheads to Taiwan. In August, a B-52 bomber was accidentally loaded with six nuclear bombs in a 1,200-kilometre flight between two bases within the United States.

"The safety, security and reliability of our nuclear weapons and associated components are of paramount importance," Gates said. "It is a tremendous responsibility and one we must and will never take lightly."

Gates blamed "systemic weaknesses," a failure of oversight and "lack of a critical self-assessment" at the Air Force for the two errors, both of which could have been prevented.

Gates also said he was launching an independent taskforce to make recommendations on how to shore up the Air Force's nuclear mission. More resignations or disciplinary action within the military branch could follow. (dpa)