President Barack Obama visited US troops in the Demilitarised Zone (DMZ) that separates the two Koreas on Sunday.

Obama arrived in South Korea to participate in the two-day global security meet on nuclear weapons that begins on Monday.

After reaching Seoul, Obama immediately flew to the DMZ in military helicopter and met over 20,000 US troops stationed there.

The US president also surveyed the highly fortified North Korea border about ten minutes from a viewing platform behind the bullet proof enclosures.

"You guys are at freedom's frontier," Obama told the US troops at the DMZ.

Take a look at Obama at the Korean border:

Obama at the DMZ
U.S. President Barack Obama looks North from South Korea along the DMZ. Reuters
Obama at the DMZ
U.S. President Barack Obama looks along the DMZ looking North from South Korea on 25/03/2012. Reuters
Obama at the DMZ
U.S. President Barack Obama looks through binoculars to see North Korea during a visit to the DMZ, north of Seoul Reuters
Obama at the DMZ
U.S. President Barack Obama shakes hands with South Korean troops at Observation Post Ouellette during a visit to the truce village of Panmunjom. Reuters
Obama at the DMZ
U.S. President Barack Obama arrives at the DMZ bordering North and South Korea. Reuters
Obama at the DMZ
North Korean flag flutters on top of a tower at the propaganda village of Gijungdong in the demilitarised zone. Reuters
Global Nuclear Security Summit
Policemen patrol in front of COEX before Nuclear Security Summit in Seoul Reuters
Global Nuclear Security Summit
U.S. President Obama shakes hands with South Korea's President Lee upon his arrival at the Blue House in Seoul. Reuters
Barack Obama South Korea North Korea