Apple CEO: We care about our workers

Cook was responding to a report in The New York Times about harsh and sometimes dangerous working conditions at Apple's main contract manufacturer, Foxconn, in China, an issue that for years has been a thorn in the company's side.

Apple responded in the past by launching independent audits and publishing the results. Earlier this month, Apple for the first time published a list of all its main suppliers.

"What we will not do -- and never have done -- is stand still or turn a blind eye to problems in our supply chain," Cook said in the email. "On this you have my word."

The email was first reported by the blog 9to5Mac and Reuters confirmed its authenticity.

The company has said it made major efforts to improve and communicate its policies after high-profile labor problems at its foreign suppliers and manufacturers, including Foxconn.

Suicides at the plants associated with Apple cast a harsh spotlight on what critics dubbed a militaristic culture in them that pushed workers to the brink to meet unceasing demand by the company.