SEOUL (REUTERS) - South Korean President Moon Jae In's approval rating has fallen to a four-month low, a poll showed on Friday (Jan 19), after a public backlash over a decision for South and North Korea to field a joint ice hockey team at next month's Winter Olympics.

Mr Moon's approval rating dropped to 67 per cent, Gallup Korea said in a statement, down from last week's 73 per cent and the second-lowest ever after the rating stood at 65 per cent in late September last year.

North and South Korea started a rare dialogue last week over the participation of North Korea in the Winter Games, and in addition to the joint ice hockey team, the two Koreas agreed on Wednesday to march under a unity flag at the Olympics.

The President's specific moves to bring together the two Koreas at the Pyeongchang Winter Olympics have sparked a sharp public backlash that has gone beyond his traditional conservative detractors to include his main support base of young South Koreans.

Friday's poll showed Mr Moon's approval rating among people in their 20s and 30s fell to 75 per cent and 82 per cent respectively, dropping by 6 percentage points and 7 percentage points compared to the previous week's rating.

Gallup Korea also said approval ratings for Mr Moon had dropped markedly among those in their 40s and below compared to those in their 50s and older. The latter are not part of Mr Moon's main support base and tend to be more conservative in South Korea's political landscape.

Mr Moon was elected to office in May last year with a high approval rating after his predecessor Park Geun Hye was removed from office over a corruption scandal.

The latest poll of 1,005 adults, was conducted this week from Tuesday to Thursday and has a margin of error of plus minus 3.1 per cent.