President Lee Myung-bak and U.S. President Barack Obama on Sunday called on North Korea to abandon plans to launch what it says is a satellite-carrying rocket next month. The two leaders met for an hour at Cheong Wa Dae ahead of the Nuclear Security Summit in Seoul.

Obama said the rocket launch plan, which is widely believed to be a cover for a long-range missile, requires a "clear, firm, precise" response, according to Cheong Wa Dae official Kim Tae-hyo.

At a joint press conference after the summit, Obama said every time North Korea violated UN Security Council resolutions, it has "resulted in further isolation, tightening of sanctions, stronger enforcement, greater support on the part of the international community for stronger enforcement. I suspect that will happen this time as well."

President Lee Myung-bak shakes hands with U.S. President Barack Obama during a joint press conference following their meeting at Cheong Wa Dae in Seoul on Sunday, on the eve of the 2012 Seoul Nuclear Security Summit.

The U.S. president said the plan violates the North's commitment, only last month in talks between Pyongyang and Washington, where the North promised to halt missile tests and uranium enrichment in return for 240,000 tons of food aid. "It would be difficult to move forward with that package" if it clings to the plan, Obama added.

Lee and Obama also touched on ongoing talks between the two allies about extending the permissible range of South Korean missiles. Lee said, "Although it was not discussed during the summit, it is being discussed between the two sides at the working level, and a conclusion will be reached soon." Obama added there are various technical problems, and many areas must be discussed at a military level rather than at the presidential level.