South Korea is set to support a UN resolution condemning North Korea's human rights record, in an abrupt reversal of its previous policy.
Seoul has faced criticism at home and abroad for its "sunshine policy"
A foreign ministry spokesman said Seoul wanted to promote human rights as well as "desperately needed" dialogue with Pyongyang following its nuclear test.
South Korea has abstained from previous votes in case it jeopardised its reconciliation policy with Pyongyang.
The draft resolution is expected to be voted on in the coming days.
The document condemns North Korea for widespread human rights abuses, which include torture, public executions and forced labour.
It also accuses the state of running large prison camps and denying any right to freedom of speech or thought.
In a statement, the South Korean foreign ministry said: "The government has decided to vote in favour [of the resolution]."
"We expect this decision will not only contribute to enhancing general human rights but also to promoting dialogue and discussion which are desperately needed especially since the nuclear test," the statement added.
South Korea has abstained from previous UN votes on this issue, citing delicate relations with its impoverished communist neighbour.
Seoul says it is continuing to pursue its so-called "sunshine policy" of reconciliation and co-operation despite the 9 October nuclear test.
But it has come under pressure from Washington to take a stronger line against the North, the BBC's Charles Scanlon in Seoul says.
Analysts say Seoul was also finding it difficult to justify its stance in the face of growing international awareness of the abuses in North Korea.
The selection of former South Korean Foreign Minister Ban Ki-Moon as new UN Secretary General may have contributed to the decision, our correspondent adds.
North Korea accuses its critics, including the United States, of using human rights to undermine its system.