Chinese hackers in March broke into the computer networks of the United States government agency that houses the personal information of all federal employees, according to senior American officials. They appeared to be targeting the files on tens of thousands of employees who have applied for top-secret security clearances. The hackers gained access to some of the databases of the Office of Personnel Management before the federal authorities detected the threat and blocked them from the network, according to the officials. 

Cyber security is set to be discussed for the first time at a meeting of NATO defence ministers next week.The Pentagon chief said Washington would press Beijing using both public diplomacy and private talks.