The influential sister of North Korean leader Kim Jong-un says they are willing to resume talks with the South if it ended its "hostile policies".

Kim Yo-jong was responding to a renewed call from the South to officially declare an end to the Korean War.

The conflict, which split the peninsula into two, ended in 1953 with an armistice and not a peace treaty.

The two countries have technically been at war ever since and locked in a sometimes tense relationship.

This week, South Korean President Moon Jae-in called for the two Koreas and their allies - the US which backs the South, and China which is the North's biggest economic partner - to declare a formal end to the conflict and bring peace to the peninsula.

The idea was initially dismissed by a top North Korean minister as "premature".

But in an unexpected statement released on Friday through state media, Ms Kim said the idea was "admirable".

However, she added that the North would only be willing to discuss the proposal if the South stopped what she called "hostile policies" towards them.

"What needs to be dropped is the double-dealing attitudes, illogical prejudice, bad habits and hostile stand of justifying their own acts while faulting our just exercise of the right to self-defence," she said in a statement.

"Only when such a precondition is met, would it be possible to sit face to face and declare the significant termination of war."