HILLARY Clinton has broken her silence over a budding controversy involving her use of personal email for work when she was secretary of state, saying she wanted the US State Department to release them swiftly.

Mrs Clinton's statement was aimed at cooling a political firestorm over allegations she inappropriately used her personal email for work while secretary of state from 2009 to 2013.

"I want the public to see my email," the potential 2016 presidential candidate said in a tweet. "I asked State to release them. They said they will review them for release as soon as possible."

The controversy has suddenly put Mrs Clinton into trouble just as she is planning to launch a bid for the Democratic presidential nomination in 2016. It has prompted some Democrats to wonder whether someone else should be their candidate to succeed President Barack Obama.

The State Department said it will review the emails provided by Mrs Clinton "using a normal process that guides such releases."

"We will undertake this review as quickly as possible. Given the sheer volume of the document set, this review will take some time to complete," spokeswoman Marie Harf said.

Mrs Clinton's tweeted statement came hours after a congressional committee investigating the 2012 attack on a US diplomatic facility in Benghazi, Libya, issued subpoenas for her emails.

The US House of Representatives' Select Committee on Benghazi demanded all communications from Mrs Clinton related to the incident, in which a US ambassador was killed.