US President Barack Obama has warned North Korea that it will "achieve nothing by threats or by provocations".
The warning comes as North Korea prepares to launch a long-range missile which Pyongyang says will put a satellite in orbit.
Obama was speaking in Seoul with South Korean President Lee Myung-bak ahead of global nuclear security talks.
The two leaders said North Korea risked further sanctions and isolation if it did not cancel its launch plans.
Lee said he and his US counterpart had "agreed to respond sternly to any provocations and threats by the North and to continually enhance the firm South Korea-US defence readiness".