US President Barack Obama arrived in Seoul on Friday amid mounting fears that North Korea is planning to carry out further nuclear tests.
Mr Obama, who flew in from Japan, was due to hold talks with South Korea’s President Park Geun-hye – but security concerns were overshadowed by the aftermath of the country’s ferry disaster.
The US president expressed his condolences over the tragedy, which left over 300 people either dead or missing presumed dead.
“As allies, but also friends, we join you in mourning the missing, and especially the young people,” Mr Obama said.
Accepting an American flag, which flew over the White House on 16 April when the disaster occurred, Ms Park drew a parallel between the way Americans pulled together after 9/11 and the resilience of South Koreans in the aftermath of their own tragedy.
“The Korean people draw great strength from your kindness,” she said.
The vast majority of the ferry victims attended a high school near Seoul. Most of the ferry’s 29-person crew survived, but 11, including the captain, have been arrested on suspicion negligence or abandoning people in need as the ferry sank. Ms Park recently blasted their actions as “tantamount to murder.”
South Korea ferry disaster
South Korea ferry disaster
1/6 South Korea ferry disaster
A woman ties a yellow ribbon dedicated to dead and missing passengers onboard sunken passenger ship Sewol to a pillar at Yellow Ribbon's Garden set up at Seoul City Hall Plaza
2/6 South Korea ferry disaster
A South Korean man walks past a well-wishing ribbon in Seoul
3/6 South Korea ferry disaster
High school student who are members of the Youth section of the Seoul Alpine Federation, climb to display a sign reading 'My dear friend I will remember you forever' while hoping for the safe return of the sunken ferry Sewol's missing passengers as they hang on a rope bridge on the Ansan mountain in Seoul
4/6 South Korea ferry disaster
High school student hold a sign reading 'My dear friend I will remember you forever' while hoping for the safe return of the sunken ferry Sewol's missing passengers as they hang on a rope bridge on the Ansan mountain in Seoul
5/6 South Korea ferry disaster
File image: A diver gets out from the sea after attempting to search for the missing passengers at the site of the sunken South Korean ferry 'Sewol' off Jindo on 26 April, 2014
6/6 South Korea ferry disaster
South Korean coast guard officers try to rescue passengers from the Sewol ferry as it sinks in the water off the southern coast near Jindo, south of Seoul, South Korea
But concerns about nuclear testing in the North were still high on the agenda with Mr Obama due to receive a military briefing at Yongdsan Garrison, where US operations in South Korea are headquartered.
Pyongyang threatened last month to conduct a fourth nuclear test, possibly while the US leader is in the region. The White House said it was keeping close tabs on activity at the North's nuclear test site, where commercial satellite imagery this week showed increased activity.
White House officials said the president did not plan to alter his itinerary because of the ferry disaster, but would probably soften warnings he had been expected to deliver about North Korea and tensions in the region with words of condolence.
In an interview with the South Korean newspaper JoongAng Ilbo, Mr Obama acknowledged that his arrival comes at a difficult time for the country.
He went on to say that another nuclear test would gain North Korea “absolutely nothing” but deeper isolation from the world. He said such a test would meet a “firm response” from the international community, without specifying the response.
Mr Obama was also due to renew his plea for countries in the region to de-escalate multiple territorial disputes with China, officials said. Seoul's key concern is about an area in the East China Sea that is effectively controlled by South Korea but falls within a controversial air defence zone that China created last year.
The US President’s overnight stay is his second stop on a four-country Asia tour that also includes visits to Malaysia and the Philippines. Mr Obama flew to Seoul from Japan, a major US ally whose relationship with South Korea has deteriorated over historical resentments stemming from World War Two.
Last month, Mr Obama brought Ms Park and her Japanese counterpart together for a trilateral meeting - he was expected to follow up on those discussions while in South Korea.
Additional reporting by Associated Press