A snappy grey suit donned by North Korean leader Kim Jong-Un's for his New Year's address has got analysts wondering whether the reclusive regime is deploying a new wardrobe as part of a diplomatic makeover for 2018.

Kim used his annual speech to warn the United States that he has a "nuclear button" on his table while offering an apparent olive branch to South Korea, saying he was prepared for talks and may send a team to the Winter Olympics there.

The softer tone and the surprisingly snazzy Western-style suit and matching grey tie -- a stark change from his usual dour Mao suits -- had analysts trying to read the unexpected sartorial signals.

"Kim Jong-Un's silver Western-style suit and horn-rimmed glasses, as well as the fact that he was not wearing a badge of his grandfather and father, shows his confidence and stability. It signals that he is in control," Professor Yang Moo-Jin of the University of North Korean Studies in Seoul told AFP.

Robert Kelly of Pusan National University described the torchbearer of the Kim dynasty as looking more like "a banker, wearing Armani".

"There has been a lot of speculation that he is trying to make North Korea look more modern and connected. His father's Mao suits looked ridiculous in the 21st century," he was quoted as saying in the New York Times.

"It’s a flimflam... Just a show."

South Korea's state-run Korea Institute for National Unification, said it appeared that Pyongyang had gone "to great lengths for the image-making".

"The change from previously darker Maoist suits to a softer-toned grey Western-style suit appears to be aimed at portraying the image of peace stressed in the speech and reflecting a relaxed state of mind following the completion of nuclear statehood," it said.

Whether it was the change in Kim's tone or wardrobe that was at work, South Korea responded favourably, reaching out to Pyongyang on Tuesday with the offer of high-level talks next week.