UN chief Ban Ki-moon and South Korean President Lee Myung-Bak vowed Saturday to together tackle any threats arising from North Korea's "gravely provocative" rocket launch planned for next month.
Ban arrived in Seoul earlier in the day for a 53-nation nuclear security summit on Monday and Tuesday, which takes place under the shadow of Pyongyang's plan to launch a rocket to purportedly put a satellite into orbit.
The United States, Australia and other nations see the move as a pretext for a long-range missile test banned by the UN.
"President Lee and Secretary-General Ban shared an understanding that North Korea's announced plan to launch a rocket is in breach of a UN Security Council resolutions," Lee's office said in a press statement.
"They expressed concerns over the launch which they agreed would be a grave provocative act against the international community." the office said.
South Korea's Yonhap news agency said both sides agreed to work closely together to deal with any threats arising from the proposed rocket launch.
In Kuala Lumpur, Ban Ki-moon said on Thursday that he would raise North Korea's planned rocket launch at the Seoul summit next week, expressing "deep concern" over the issue.
Pyongyang has said any South Korean attempt to address the North's nuclear programme at the March 26-27 summit would be seen as a declaration of war.
But the programme and the rocket launch were expected to be hot topics on the sidelines of the meeting, which will see US President Barack Obama and other world leaders meet to discuss nuclear security issues.
A UN Security Council resolution passed after the North staged missile and nuclear tests in 2009 bans a ballistic missile launch for any purpose.
Ban said in Kuala Lumpur that it could also undermine recent positive signs on long-running diplomatic efforts to end North Korea's nuclear programme.