US Secretary of Defence Ashton Carter has arrived in South Korea amid simmering tensions in the Korean peninsula.
Carter, who is on his first trip to Asia since taking over as defence chief, arrived in Seoul after wrapping up a three-day visit to Japan.
Carter will hold talks with his South Korean counterpart on how to handle the growing threats from North Korea.
It is unclear if the deployment of the Terminal High Altitude Area Defence (THAAD) system by the US in the Korean peninsula will feature during the discussions. Washington has been keen on stationing the missile-defence system but neighbouring countries such as China and Russia have expressed concern.
Carter will meet US troops at the Osan Air Base in Pyeongtaek shortly. He will meet South Korean President Park Geun-hye on Friday, 10 April, and hold bilateral talks with Defence Minister Han Min-koo after that.
Carter will also become the first American defence chief to visit the Cheonan memorial for South Korean sailors. The naval corvette sank in the Yellow Sea killing 46 South Koreans in March 2010. North Korea has been blamed for the incident but Pyongyang officially denies any hand.
"The US insisted on Carter visiting the Cheonan memorial. It will be a chance to show North Korea that South Korea and the US are determined to stand together against any provocation," a South Korean official was quoted as saying by the Chosun Ilbo daily.