President Donald Trump shook hands with Kim Jong Un on Sunday and took 20 steps into North Korea, making history as the first sitting US leader to set foot in the hermit kingdom.

The meeting at the Korean Demilitarized Zone -- their third in person -- came a day after Trump raised the prospect of a border handshake in a tweet and declared he'd have "no problem" stepping into North Korea. While inside North Korean territory, they shook hands and patted each other's backs before returning across the border to the South.

Trump said he was "proud to step over the line" and thanked Kim for the meeting.

The US President said he's invited Kim to the White House, and both leaders have agreed to restart talks after nuclear negotiations stalled.

"We just had a very, very good meeting with Chairman Kim," Trump told reporters after parting with Kim at the Korean border.

The two leaders meet at the demilitarized zone separating the two Koreas, in Panmunjom on Sunday.
The two leaders meet at the demilitarized zone separating the two Koreas, in Panmunjom on Sunday.
Kevin Lemarque/Reuters
Trump became the first sitting US president to step into North Korea on Sunday, June 30.
Trump became the first sitting US president to step into North Korea on Sunday, June 30.
Susan Walsh/AP
Trump makes history as he steps onto the northern side of the Military Demarcation Line that divides North and South Korea on June 30. Kim looks on as Trump becomes the first sitting US President to walk into South Korea.
Trump makes history as he steps onto the northern side of the Military Demarcation Line that divides North and South Korea on June 30. Kim looks on as Trump becomes the first sitting US President to walk into South Korea.
Brendan Smialowski/AFP/Getty Images
North Korea's leader Kim Jong Un walks to greet US President Donald Trump at the Military Demarcation Line that divides North and South Korea, in the Joint Security Area (JSA) of Panmunjom in the Demilitarized Zone (DMZ) on Sunday, June 30.
North Korea's leader Kim Jong Un walks to greet US President Donald Trump at the Military Demarcation Line that divides North and South Korea, in the Joint Security Area (JSA) of Panmunjom in the Demilitarized Zone (DMZ) on Sunday, June 30.
Brendan Smialowski/AFP/Getty Images
North Korean security agents keep watch south of the Military Demarcation Line that divides North and South Korea, as Trump and Kim meet in the Joint Security Area of Panmunjom in the Demilitarized zone on June 30.
North Korean security agents keep watch south of the Military Demarcation Line that divides North and South Korea, as Trump and Kim meet in the Joint Security Area of Panmunjom in the Demilitarized zone on June 30.
Brendan Smialowski/AFP/Getty Images
Kim and Trump shake hands during a meeting on the south side of the Military Demarcation Line that divides North and South Korea on June 30.
Kim and Trump shake hands during a meeting on the south side of the Military Demarcation Line that divides North and South Korea on June 30.
Brendan Smialowski/AFP/Getty Images
After shaking hands and patting each other's backs while inside North Korean territory, the leaders walked together back across the line into South Korea.
After shaking hands and patting each other's backs while inside North Korean territory, the leaders walked together back across the line into South Korea.
Kevin Lamarque/Reuters
Kim speaks as he stands with Trump south of the Military Demarcation Line that divides North and South Korea, in the Joint Security Area of Panmunjom in the Demilitarized zone on June 30.
Kim speaks as he stands with Trump south of the Military Demarcation Line that divides North and South Korea, in the Joint Security Area of Panmunjom in the Demilitarized zone on June 30.
Brendan Smialowski/AFP/Getty Images
Trump steps onto the northern side of the Military Demarcation Line that divides North and South Korea, on Sunday, June 30, as Kim looks on.
Trump steps onto the northern side of the Military Demarcation Line that divides North and South Korea, on Sunday, June 30, as Kim looks on.
Brendan Smialowski/AFP/Getty Images
White House Senior Advisors Ivanka Trump and Jared Kushner, walk in the border village of Panmunjom in the Korean Demilitarized Zone in South Korea, on Sunday, June 30.
White House Senior Advisors Ivanka Trump and Jared Kushner, walk in the border village of Panmunjom in the Korean Demilitarized Zone in South Korea, on Sunday, June 30.
Susan Walsh/AP
People at the Seoul Railway Station watch a news program on a TV screen showing Trump and Kim at the border village of Panmunjom on June 30.
People at the Seoul Railway Station watch a news program on a TV screen showing Trump and Kim at the border village of Panmunjom on June 30.
Ahn Young-joon/AP
South Korean President Moon Jae-in meets with North Korean leader Kim Jong Un, alongside President Trump at the truce village of Panmunjom in the Korean Demilitarized Zone, on Sunday, June 30.
South Korean President Moon Jae-in meets with North Korean leader Kim Jong Un, alongside President Trump at the truce village of Panmunjom in the Korean Demilitarized Zone, on Sunday, June 30.
YONHAP/EPA-EFE/Shutterstock
Trump meets US service members stationed in South Korea in Osan Air Base, following his meeting with Kim at the Joint Security Area in Panmunjom in the Korean Demilitarized Zone on June 30.
Trump meets US service members stationed in South Korea in Osan Air Base, following his meeting with Kim at the Joint Security Area in Panmunjom in the Korean Demilitarized Zone on June 30.
Brendan Smialowski/AFP/Getty Images
Trump views North Korea from from Observation Post Ouellette at Camp Bonifas in South Korea on Sunday, June 30.
Trump views North Korea from from Observation Post Ouellette at Camp Bonifas in South Korea on Sunday, June 30.
Susan Walsh/AP
Trump talks with South Korean President Moon and views North Korea from Observation Post Ouellette at Camp Bonifas in South Korea.
Trump talks with South Korean President Moon and views North Korea from Observation Post Ouellette at Camp Bonifas in South Korea.
Susan Walsh/AP
Trump and Moon visit an observation post in the Korean Demilitarized Zone separating North and South Korea on Sunday, June 30.
Trump and Moon visit an observation post in the Korean Demilitarized Zone separating North and South Korea on Sunday, June 30.
Brendan Smialowski/AFP/Getty Images
Trump and Moon visit an observation post in the Joint Security Area at Panmunjom in the Demilitarized Zone separating North and South Korea on June 30.
Trump and Moon visit an observation post in the Joint Security Area at Panmunjom in the Demilitarized Zone separating North and South Korea on June 30.
Brendan Smialowski/AFP/Getty Images