U.S. Vice President Mike Pence arrived in South Korea on Sunday afternoon, roughly nine hours after a failed missile launch attempt by North Korea earlier in the day.
The US Pacific Command said it tracked a missile launch on Sunday night and said the missile blew up nearly immediately.
North Korea regularly launches short-range missiles, but it is also developing mid-range and long-range missiles meant to target USA troops in Asia and, eventually, the US mainland.
In response to a question, Chinese Foreign Ministry spokesman Geng Shuang also said: "It's not hard to see that ever since the United States and Republic of Korea chose to deploy THAAD, the situation has not become harmonious but has become more tense".
President Donald Trump's vice president arrived in the region a day after North Korea celebrated the birth anniversary of the country's late founder with a military parade showing off missiles and military hardware.
However, Reuters also reported that China had cancelled regularly-scheduled flights to the North's capital, Pyongyang.
"The type of missile is still being assessed", the U.S. Pacific Command says in an emailed statement. "I have great confidence that China will properly deal with North Korea", he tweeted."If they are unable to do so, the US, with its allies, will!" Pence was briefed on the situation while flying to South Korea, reporter Jihye Leetells our newscast.
On Tuesday President Trump tweeted that the U.S. would not be afraid to act alone on North Korea if Beijing does not help.
The U.S. Pacific Command said the missile "blew up nearly immediately", adding the type of missile was being analyzed.
Along with the deployment of the US aircraft carrier and other vessels into waters off the Korean Peninsula, thousands of USA and South Korean troops, tanks and other weaponry were deployed last month in their biggest joint military exercises.
Pence's first trip to South Korea will carry personal meaning as well.
The U.S. Pacific Command said in a statement that Sunday's missile exploded on launch.
A USA nuclear-powered aircraft carrier strike group is also heading for the region.
With South Korean presidency due to change within the month due to the upcoming election on May 9, the White House underlined that Pence would not be meeting any of the presidential candidates.
Sinpo, where the launch took place, is the site of a North Korean submarine base and where the North has tested the submarine-launched ballistic missile (SLBM) it is developing. Recent satellite imagery suggests the country could conduct another underground nuclear test at any time.