Donald Trump says he would "bring back a hell of a lot worse than waterboarding” if he becomes president
US Republican presidential contender Marco Rubio has come under attack from his rivals who are challenging him for the nomination to run for the White House.
In a fiery television debate on ABC, ahead of Tuesday's New Hampshire primary, the senator was accused of being too inexperienced by Governor Chris Christie.
Governor Christie suggested Rubio had "not been involved in a consequential decision where you had to be held accountable. You simply haven't".
Christie - who CNN describes as being on a "do-or-die last stand" in New Hampshire - also accused his rival of having a "memorised speech" to recite in public.
Meanwhile, seven years after the US banned waterboarding as an interrogation technique, Donald Trump admitted he would revive its use if he were American president.
The billionaire suggested he would "bring back a hell of a lot worse than waterboarding”.
Speaking during the ABC debate, Trump remained largely at odds with the other presidential candidates ahead of the New Hampshire primary.
He was also booed by the audience after suggesting "donors and special interests... the people that are putting up the money" had the tickets to televised debates.
A CNN/WMUR poll earlier this week showed Donald Trump with a clear lead ahead of the New Hampshire primaries with 28%, compared to 17% for Marco Rubio and 13% each for Ted Cruz and John Kasich.
The Republican Iowa caucus was won by Ted Cruz with 28% of the vote. Donald Trump followed in second with 24%, while Marco Rubio was close behind them both with 23%.