The Pakistani military says it is training 8,000 additional people to protect the country's nuclear arsenal.
The United States fears Pakistan's nuclear program could be vulnerable to penetration by Islamist militants at war with the West.
Those fears were heightened by a recent article in The Atlantic magazine that quoted unnamed officials as saying Pakistan transports nuclear weapons components around the country in delivery vans with little security to avoid detection - a claim denied by Islamabad.
Pakistan rarely reveals details about its nuclear program or the security around it. The military's announcement Sunday that it is training 8,000 additional guards could be seen as a response to the magazine article.