Warning North Korea from its doorstep, President Barack Obama said Pyongyang risks deepening its isolation in the international community if it proceeds with a planned long-range rocket launch. "North Korea will achieve nothing by threats or provocations," Obama said during a news conference Sunday in Seoul, South Korea, where he was to attend a nuclear security summit. Obama spoke fresh off his first visit to the tense Demilitarized Zone, the heavily patrolled no-man's land between North and South Korea, where he peered long and hard at the isolated North. "It's like you're in a time warp," Obama said. "It's like you're looking across 50 years into a country that has missed 40 years or 50 years of progress." From the DMZ, Obama returned to Seoul for a private meeting with South Korean President Lee Myung-bak. Both leaders warned there would be consequences if North Korea proceeds with its plans to launch a satellite using a long-range rocket next month, a move the U.S. and other powers say would violate a U.N. ban on nuclear and missile activity because the same technology could be used for long-range missiles. Obama said the launch would jeopardize a deal for the U.S. to resume stalled food aid to North Korea and may result in the tightening of harsh economic sanctions on the already-impoverished nation.