South Korea's offer to send athletes to a North Korean ski resort for joint training ahead of next month's Olympics risks giving Kim Jong Un's regime legitimacy and some much-needed cash, North Korean defectors and experts say.

Already facing criticism for plans to march under a unity flag and field a combined Korean ice hockey team, the administration of South Korean President Moon Jae-in may come under further pressure if it is seen to be endorsing Kim's luxury getaway on North Korea's east coast.

"The idea of joint training could be used as a propaganda tool to rationalize how far-sighted Kim Jong Un was in making what was actually an anachronistic decision to build the ski resort at a time when ordinary citizens are starving to death," said Kim Sung-han, a former South Korean vice foreign minister.