US President Barack Obama says he does not consider the Sony hack an act of war but an act of cyber vandalism.

The US is weighing up how to respond to the attack, which prompted Sony to withdraw the movie The Interview, which had been set for release during the holiday season.

The movie, starring Seth Rogen and James Franco, parodies North Korea and its leader Kim Jong-Un.

"I don't think it was an act of war. I think it was an act of cyber vandalism that was very costly, very expensive," the US President said in a TV interview set for broadcast later on Sunday.

"We take it very seriously. We will respond proportionately."

Speaking to CNN, Mr Obama also said his government was considering putting North Korea back on a US list of countries that sponsor terrorism.

North Korea spent two decades on the list until the Bush administration removed it in 2008 during nuclear negotiations. Some politicians in the US have called for the designation to be restored following the hack.

Only Iran, Sudan, Syria and Cuba remain on the list, which triggers sanctions that limit US aid, defence exports and certain financial transactions.

The US believes that Pyongyang is behind the hack attack, which also involved the embarrassing leak of scores of private emails of Hollywood stars and industry executives.

North Korea insists it had nothing to do with the cyber-attack on Sony and has proposed a joint investigation with the US.

The decision to pull the film was made after the group claiming responsibility for the cyber-attack - the self-styled Guardians of Peace - made terrorist threats against US cinemas that prepared the show the movie.

It sparked anger and criticism among Hollywood actors, with some saying it set a dangerous precedent.

Mr Obama had previously called the decision a mistake.

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