U.S. Secretary of State John Kerry has started a tour of Asia, where he plans to push North Korea to give up its nuclear ambitions and China to reduce regional tensions.
The trip is Kerry's fifth visit to Asia since becoming the top U.S. diplomat last year. It will include stops in South Korea on Thursday, China on Friday, and Indonesia on Saturday.
Washington has been critical of what it sees as China's attempts to gain control over contested parts of the East and South China Seas.
Ahead of Kerry's arrival in Seoul, a U.S. official said it is "unwise in the extreme for China" to take disruptive and destabilizing actions. The official warned Beijing should "do nothing to upend the status quo."
The Obama administration last week called on China to clarify or amend its vast maritime claims, suggesting they may be inconsistent with international law.
Kerry also is expected to encourage Beijing to put more pressure on its ally North Korea to scale back its nuclear weapons program.
The U.S. official says Kerry would like North Korea to rejoin stalled six-nation nuclear talks, but suggested the North would have to take "convincing steps" in order to do so.
North Korea will also be the main focus of Kerry's stop in Seoul, which this week held its highest-level talks in seven years with Pyongyang.
Inter-Korean ties have shown signs of improvement, but are expected to be strained later this month when U.S.-South Korean war drills begin.
North Korea says the annual exercises could prompt it to cancel reunions set for late February between families separated by the Korean War.
The drills have also complicated U.S. efforts to win freedom for Korean-American Kenneth Bae, who is detained in a North Korean labor camp.
Pyongyang has twice withdrawn an invitation for a senior U.S. diplomat to visit and negotiate the release of the Christian missionary.
In Indonesia, the last leg of Kerry's trip, climate change is expected to be a major focus. He is expected to deliver a major speech on climate change in the archipelago nation, which analysts say is especially vulnerable to climate change.
From Jakarta, Kerry will head Monday to the United Arab Emirates to meet Gulf leaders on Iran nuclear talks, Syria's civil war, and Middle East peace talks.
Some have accused the White House of focusing on the Middle East at the expense of its so-called economic and military "pivot" to Asia.