President Barack Obama visited US troops on the tense Korean border on Sunday.
Obama is in South Korea as part of the global summit on nuclear security in Seoul, beginning on Monday which will be attended by leaders from over 50 countries.
After arriving in Seoul, Obama flew by helicopter to the Demilitarised Zone (DMZ) separating the Koreas to meet US troops stationed there. Over 20,000 US soldiers are stationed at the DMZ.
The US president had a binocular vision at the heavily fortified borders of North Korea on Sunday.
Former presidents Ronald Reagan, Bill Clinton and George Bush also had visited the DMZ.
The two-day summit which is meant to prevent access to nuclear weapons to militants and criminal groups will also see Obama lobbying with Russia and China to put more pressure on Pyongyang to cancel its rocket launch.
Earlier, North Korea had announced its decision to launch a satellite to mark the 100th birth anniversary of its founder Kim Il-sung by the middle of April.
The move by Pyongyang is viewed as a violation of its promise to halt long-range missile launches, nuclear tests and uranium enrichment in order to ensure a deal to access US food aid.
Japan has already declared that it will intercept and bring down the North Korean rocket if it flies towards Japan.
North Korea and Iran are not on the list of countries participating in the security summit.