Now playing
01:04
US defense secretary arrives in South Korea
Now playing
01:26
Sarah Sanders: I was kicked out of restaurant
U.S. Secretary of Homeland Security Kirstjen Nielsen speaks on migrant children being separated from parents at the southern border during a White House daily news briefing at the James Brady Press Briefing Room of the White House June 18, 2018 in Washington, DC. Nielsen joined White House Press Secretary Sarah Sanders at the daily news briefing to answer questions from members of the White House Press Corps.
PHOTO: Alex Wong/Getty Images
U.S. Secretary of Homeland Security Kirstjen Nielsen speaks on migrant children being separated from parents at the southern border during a White House daily news briefing at the James Brady Press Briefing Room of the White House June 18, 2018 in Washington, DC. Nielsen joined White House Press Secretary Sarah Sanders at the daily news briefing to answer questions from members of the White House Press Corps.
Now playing
01:18
Protesters confront Secy. Nielsen at restaurant
Richard Grenell, nominee to be US ambassador to Germany, testifies during a Senate Foreign Relations Committee hearing on Capitol Hill in Washington, DC, September 27, 2017. (SAUL LOEB/AFP/Getty Images)
PHOTO: SAUL LOEB/AFP/Getty Images
Richard Grenell, nominee to be US ambassador to Germany, testifies during a Senate Foreign Relations Committee hearing on Capitol Hill in Washington, DC, September 27, 2017. (SAUL LOEB/AFP/Getty Images)
Now playing
00:42
US envoy remarks to Brietbart provoke backlash
KANAB, UT - MAY 10: U.S. Secretary of the Interior Ryan Zinke talks to reporters before departing Kanab Airport on May 10, 2017 in Kanab, Utah. Zinke has been in the state of Utah since Sunday talking with state and local officials and touring the Bears Ears National Monument and Grand Staircase-Escalante National Monument, to help determine their future status under the Trump Administration. (Photo by George Frey/Getty Images)
PHOTO: George Frey/Getty Images
KANAB, UT - MAY 10: U.S. Secretary of the Interior Ryan Zinke talks to reporters before departing Kanab Airport on May 10, 2017 in Kanab, Utah. Zinke has been in the state of Utah since Sunday talking with state and local officials and touring the Bears Ears National Monument and Grand Staircase-Escalante National Monument, to help determine their future status under the Trump Administration. (Photo by George Frey/Getty Images)
Now playing
01:41
Zinke claims to be geologist, again
PHOTO: CNN
Now playing
02:39
All the Trump officials who threatened to quit
CIA nominee Gina Haspel is sworn in during a confirmation hearing of the Senate Intelligence Committee on Capitol Hill, Wednesday, May 9, 2018 in Washington. (AP/Alex Brandon)
PHOTO: Alex Brandon/AP
CIA nominee Gina Haspel is sworn in during a confirmation hearing of the Senate Intelligence Committee on Capitol Hill, Wednesday, May 9, 2018 in Washington. (AP/Alex Brandon)
Now playing
02:33
Haspel balks on morality of torture program
PHOTO: Getty Images
Now playing
02:26
Trump's Cabinet faces travel scrutiny
david jolly
PHOTO: CNN
david jolly
Now playing
00:46
Ex-lawmaker rips Trump's 'first-rate grifters'
US Secretary of Housing and Urban Development Ben Carson speaks to employees on his first day at the Department of Housing and Urban Development March 6, 2017 in Washington, DC. / AFP PHOTO / Brendan Smialowski        (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)
PHOTO: BRENDAN SMIALOWSKI/AFP/Getty Images
US Secretary of Housing and Urban Development Ben Carson speaks to employees on his first day at the Department of Housing and Urban Development March 6, 2017 in Washington, DC. / AFP PHOTO / Brendan Smialowski (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)
Now playing
02:58
Complaint filed over Carson's office expenses
david jolly
PHOTO: CNN
david jolly
Now playing
00:58
Jolly: No accountability in this administration
Interior Secretary Ryan Zinke delivers a speech billed as "A Vision for American Energy Dominance" at the Heritage Foundation on September 29, 2017 in Washington, DC.
PHOTO: Mark Wilson/Getty Images
Interior Secretary Ryan Zinke delivers a speech billed as "A Vision for American Energy Dominance" at the Heritage Foundation on September 29, 2017 in Washington, DC.
Now playing
03:11
Interior secretary's trips may have violated law
Now playing
00:46
Trump: I'm not undercutting Tillerson
PHOTO: Drew Angerer/Getty Images
Now playing
03:10
Bannon out as White House chief strategist
petersen nominee 02
PHOTO: Senate TV
petersen nominee 02
Now playing
02:25
Trump nominee can't answer basic law questions
Assistant to the US President Donald Trump Anthony Scaramucci takes part in a meeting on the theme "Monetary Policy: Where Will Things Land?" on the opening day of the World Economic Forum, on January 17, 2017 in Davos.
PHOTO: FABRICE COFFRINI/AFP/Getty Images
Assistant to the US President Donald Trump Anthony Scaramucci takes part in a meeting on the theme "Monetary Policy: Where Will Things Land?" on the opening day of the World Economic Forum, on January 17, 2017 in Davos.
Now playing
02:34
Scaramucci: Priebus a 'paranoid schizophrenic'

Story highlights

Defense Secretary James Mattis makes first overseas trip as Pentagon chief

He says he'll listen to South Korean leaders before deciding on US policy toward North

(CNN) —  

New US Defense Secretary James Mattis on Thursday defended the planned deployment of a missile defense system in South Korea, saying only North Korea had anything to fear from it.

After arriving at the Osan Air Base outside Seoul, Mattis said Pyongyang’s “provocative behavior” was the only reason the US-developed system was on the agenda.

South Korea’s decision to deploy the Terminal High Altitude Area Defense anti-missile system, known as THAAD, has drawn sharp criticism from China, which sees it as part of a broader US strategy to extend its military alliance network from Japan all the way down to the South China Sea.

“There is no other nation that needs to be concerned about THAAD other than North Korea if they’re engaged in something that’s offensive,” Mattis said.

On Thursday afternoon, Mattis met with acting South Korean President Hwang Kyo-ahn in Seoul and reiterated the strength of the US-South Korean alliance.

“I talked to President Trump and he wanted to make a very clear statement about the priority that we place on this alliance between our two nations,” the US defense chief said.

“Our new administration inherits a very strong, trusted relationship between our two countries, and it’s our commitment to make it even stronger.”

01:01 - Source: CNN Business
Watch old photos come to life using AI
PHOTO: MyHeritage
Now playing
01:01
Watch old photos come to life using AI
PHOTO: CNN/Getty Images
Now playing
06:46
McEnany says she expected 'peaceful' rally on January 6. Keilar rolls the tape
Now playing
01:26
No, Tom Cruise isn't on TikTok. It's a deepfake
PHOTO: ABC's "Jimmy Kimmel Live
Now playing
02:02
Eddie Murphy, Arsenio Hall reunite in 'Coming 2 America'
PHOTO: Courtesy AirlingRatings.com
Now playing
03:06
Virgin Atlantic CEO: We support Covid vaccine passports
Now playing
01:19
Warren proposes wealth tax: 'It's time for them to pay a fair share'
Now playing
01:43
Marriott CEO: Vaccinations are 'the key' to travel recovery
Now playing
01:23
'There should be no threats': Biden's message to union-busters
Ashley Vanderbilt Former QAnon believer
PHOTO: CNN
Ashley Vanderbilt Former QAnon believer
Now playing
07:40
Former QAnon believer shares bonkers conspiracy theory about Biden
snl.fauci.vaccine.orig_00005420.png
snl.fauci.vaccine.orig_00005420.png
Now playing
01:24
'SNL' has 'Dr. Fauci' helping people get vaccinated
A file image of the "THAAD" anti-missile defense rocket.
PHOTO: Getty Images
A file image of the "THAAD" anti-missile defense rocket.
Now playing
00:48
What is THAAD?
PHOTO: MyHeritage
Now playing
01:01
Watch old photos come to life using AI
PHOTO: CNN/Getty Images
Now playing
06:46
McEnany says she expected 'peaceful' rally on January 6. Keilar rolls the tape
Now playing
01:26
No, Tom Cruise isn't on TikTok. It's a deepfake
PHOTO: ABC's "Jimmy Kimmel Live
Now playing
02:02
Eddie Murphy, Arsenio Hall reunite in 'Coming 2 America'
PHOTO: Courtesy AirlingRatings.com
Now playing
03:06
Virgin Atlantic CEO: We support Covid vaccine passports
Now playing
01:19
Warren proposes wealth tax: 'It's time for them to pay a fair share'
Now playing
01:43
Marriott CEO: Vaccinations are 'the key' to travel recovery
Now playing
01:23
'There should be no threats': Biden's message to union-busters
Ashley Vanderbilt Former QAnon believer
PHOTO: CNN
Ashley Vanderbilt Former QAnon believer
Now playing
07:40
Former QAnon believer shares bonkers conspiracy theory about Biden
snl.fauci.vaccine.orig_00005420.png
snl.fauci.vaccine.orig_00005420.png
Now playing
01:24
'SNL' has 'Dr. Fauci' helping people get vaccinated

Mattis’ arrival in South Korea comes at a time of relative quiet from Kim Jong Un’s regime, which hasn’t tested a ballistic missile since October 20 after firing off projectiles at a record rate earlier in 2016.

The question North Korea watchers are asking: How long will Kim keep his missile program grounded?

Some analysts expect testing to resume soon.

“They have a wonderful tradition of greeting every new US president with a bit of fireworks, sometimes a nuclear test, sometimes ICBM launch, and they’re not going to break this tradition,” Korean studies professor Andrei Lankov of Kookmin University in Seoul told CNN.

But Bruce Bennett of the Rand Corp. think tank said Kim’s testing hiatus is focused not on Washington, but on Seoul and the recent impeachment of President Park Geun-hye in a corruption scandal.

Her fate is now before South Korea’s Constitutional Court. A decision against her could trigger elections earlier than the mandated December 20 deadline.

“I believe that North Korea’s No. 1 objective between now and the ROK presidential election is to ensure that the new South Korean president will be a progressive and certainly not a conservative,” Bennett said, using the acronym for the Republic of Korea.

“But any provocations that it commits would give support to conservative candidates,” the senior defense analyst said.

01:27 - Source: CNN
North, South Korean leaders to meet again