The US congresswoman shot in the head in Arizona has regained her ability to speak just a month after the mass shooting in which six people died.

Gabrielle Giffords, who was shot at a public meeting in Tucson, is speaking "more and more", according to her spokesman – the first official confirmation she has regained her speech.

The spokesman said he did not know exactly what her first words were, but one morning at breakfast she asked for toast.

Referring to her rehabilitation at University Medical Centre in Tucson, Giffords's spokesman said: "She's working very hard and it's paying off. We're elated at this. We always knew Gabby is a fighter and that she's not going to let this thing win. And you know, every day is proof of that."

Doctors hope she will be well enough to attend her husband's scheduled launch into space on the final mission of the shuttle Endeavour in April, CBS News reported. Mark Kelly is the commander of Endeavour's final flight. In a Facebook post on Tuesday, Kelly said his wife had her appetite back and was eating three times a day.

Six people, including a nine-year-old girl, were killed in the rampage on 8 January and 13, including Giffords, were injured. The suspected gunman, Jared Loughner, last month pleaded not guilty to trying to assassinate Giffords and two of her aides.