Image copyright AP Image caption South Korea, which hosts more than 28,000 US troops, remains technically at war with North Korea

The US will maintain control of South Korean troops in the event of war with the North, the two sides say, delaying again a long-planned command transfer.

Both sides attributed the delay to "an evolving security environment" and an "intensifying" threat from Pyongyang.

The transfer had been due to take place in 2012 and was then delayed until 2015. No new date has been set for it to occur.

The status quo is a legacy of the Korean War.

Since the 1950-53 conflict ended, operational control of both US and local forces in the event of a war breaking out in South Korea has rested with a US general.

South Korea retains peace-time control of its forces, and discussions on a transfer of power back to Seoul in the event of a war have been ongoing for several years.

Speaking after meeting his South Korean counterpart Han Min-koo at the Pentagon, US Defence Secretary Chuck Hagel said the move would "ensure that when the transfer does occur, Korean forces have the necessary defensive capabilities to address an intensifying North Korean threat".

Mr Han said North Korean provocations and its ongoing development of missiles and nuclear weapons had left the security situation on the Korean peninsula "more precarious than ever".

An unidentified South Korean defence ministry official cited by the Yonhap news agency said both sides expected the transfer would come in the mid-2020s when South Korea had obtained "key assets" and was "equipped with core military capabilities to lead the combined defence posture".

The two Koreas remain technically at war, because the Korean War ended in an armistice and not a peace treaty.

North Korea has conducted three nuclear tests in recent years, plus several rocket launches seen as tests of long-range missile technology.

The US has more than 28,000 troops in South Korea.