UNITED NATIONS, United States (AFP) - North Korea has lodged a formal protest at the United Nations against a Hollywood comedy about an assassination bid on leader Kim Jong Un and asked Washington to block the film's release.

The Interview stars Seth Rogen and James Franco as two tabloid television journalists who land an interview with Kim in Pyongyang and are then tasked by the CIA with killing him.

The film is due to be released in the United States on Oct 14.

In a letter addressed to UN Secretary General Ban Ki Moon, and seen on Wednesday, North Korea's UN envoy Ja Song Nam says allowing the film to be made and seen constitutes "the most undisguised sponsoring of terrorism as well as a war action."

"The US authorities should take immediate and appropriate action to ban the production and distribution of the film, otherwise it will be fully responsible for encouraging and sponsoring terrorism," the letter says.

North Korea asked that the letter be circulated as an official document to members of the UN General Assembly and Security Council for their consideration.

Last month, North Korea denounced the film as a "wanton act of terror" and warned of a "merciless response" unless it were pulled from distribution.

In a statement carried by North Korea's official KCNA news agency, a foreign ministry spokesman said the film was the work of "gangster moviemakers" and should never be shown.

Rogen poked fun at the threat on Twitter, writing: "People don't usually wanna kill me for one of my movies until after they've paid 12 bucks for it." The Interview is not the first Hollywood film to mock a North Korean leader.

In the 2004 satirical action comedy Team America, Kim's father Kim Jong Il was portrayed as a speech-impaired, isolated despot.