South Korea wrested one-upmanship from the belligerent North on Monday by issuing a stern warning that it might shoot down a rocket that Pyongyang is planning to launch next month.

We are studying measures such as tracking and shooting down (parts) of a North Korean missile in case they stray out of their normal trajectory a vice-spokesman at the Defense Ministry said, NPR reported.

Earlier on Sunday, U.S. President Barack Obama had joined South Korean President Lee Myung-bak in asking Pyongyang to halt the launch of the rocket, which South believes would violate its territory.

North Korea plans to launch the rocket around mid-April when it would be marking new leader Kim Jong Un's 100 days in power.

South Korea said on Monday it has credible information that the North is going ahead with preparations for a launch and that the main body of the rocket has been moved into a building at a site near the village of Tongchang-ri in North Phyongan province, NPR reported.

Meanwhile Obama asked Chinese Premier Hu Jintao to rein in North Korea, adding that both countries have a common interest in addressing the nuclear standoff in Asia.

Meeting Hu on the sidelines of a global nuclear security summit in Seoul, Obama said China should help control its Communist ally instead of turning a blind eye to its nuclear defiance Reuters reported.

The President warned of more stringent sanctions if Pyongyang went ahead with a rocket launch next month.

Obama said on Sunday the U.S. would have to reconsider the deal agreed last month to send food aid to North Korea if the nuclear armed state went ahead with the launch.

North Korea has insisted the rocket will not violate South territory and that a new southerly flight path is meant to avoid other countries.