Clinton in S Korea amid tensions
US Secretary of State Hillary Clinton is travelling to South Korea, amid rising tension on the Korean peninsula.
Seoul is hopeful that the new US administration will be able to restart the denuclearisation talks with North Korea, which stalled late last year.
But just hours before her arrival in Seoul, North Korea said its troops were "fully ready" for war with the South.
Mrs Clinton's visit also comes amid speculation the North may be preparing to test-fire a long-range missile.
The US secretary of state has said such a move would be "extremely unhelpful", and warned against any provocative action, saying Washington would be watching closely.
Mrs Clinton arrives in Seoul late on Thursday and will hold talks with South Korea's top leaders on Friday, before flying on to Beijing.
South Korea wants the US to help restart six-party talks - which also include China, Japan, Russia, and North Korea - aimed at ending Pyongyang's nuclear ambitions.
The BBC's state department correspondent, Kim Ghattas, says that the North's sabre-rattling over the past few weeks is seen as an attempt to grab the attention of the Obama administration and improve its bargaining position when the talks eventually resume.
When Mrs Clinton arrives in Seoul, it is the North Koreans who will be watching closely, listening to her every statement to determine their next move, our correspondent says.
Mrs Clinton is heading to Seoul after a visit to Indonesia - the world's most populous Muslim country - where she said the US was seeking a new kind of dialogue with the Muslim world.
In addition to talks with Indonesian leaders, Mrs Clinton appeared on a youth music TV show.
She joked about her poor singing abilities - but she also used her appearance to stress that Washington wants to address concerns over its policies in the Middle East and elsewhere.
Many Indonesians have been deeply troubled by US policy in the Middle East and the invasions of Iraq and Afghanistan.
Mrs Clinton also announced her intention to attend a donors' pledging conference for rebuilding Gaza, to be held in Egypt in early March.
South Korea wants US help to restart denuclearisation talks with North
North Korea maintains one of the world's biggest standing armies