As part of his 3 day official visit to the Republic of Korea, U.S. President Barack Obama on Sunday paid his first visit to the Demilitarized Zone  around the tense border between the two Koreas. His visit aims to highlight Washington's security commitment to its ally. Obama, who arrived in Seoul earlier in the day to attend the two-day Nuclear Security Summit which opens on Monday, held talks with his Korean counterpart Lee Myung-bak on Pyongyang’s plan to launch a rocket- mounted satellite. Tension is mounting between the two Koreas as the North announced its planned launch of sateliite Kwangmyongsong-3 next month. The US said the launch will make food aid hard to be realized. But Pyongyang claimed the launch will abide by international norms and is its legitimate rights.