SEOUL (REUTERS) - South Korea and China agreed on Monday recent nuclear activity by North Korea posed a serious threat to the peace and stability of the region and Pyongyang must not conduct a nuclear test, the South said after a meeting of their top diplomats.
Renewed activity at North Korea's nuclear test site has indicated Pyongyang may be preparing a fourth nuclear test in contravention of UN sanctions.
Analysis suggested the North may be close to miniaturising a nuclear warhead to mount on a missile, alarming regional powers that have for two decades tried to rein in Pyongyang's atomic programme.
Chinese Foreign Minister Wang Yi held talks with South Korea's Yun Byung Se to discuss the North's nuclear programme and also an upcoming visit by Chinese President Xi Jinping to Seoul this year, South Korea's foreign ministry said.
"The two ministers agreed to step up cooperation based on the united position that they object to the North's nuclear test and that recent nuclear activities by the North pose a serious threat to the peace and stability of the Korean peninsula and the region," South Korea's foreign ministry said.
However China, North Korea's lone major ally, is usually very guarded in its opinion on Pyongyang's nuclear programme, usually expressing its desire for a nuclear-free "Korean peninsula", careful not to be seen to be taking sides.
Mr Wang said before his meeting with Yun that it was important for six regional partners, including the United States and North Korea, to work to resume the so-called six-party talks aimed at ending the North's nuclear programme.
The talks produced an agreement in 2005 to provide the impoverished North with economic aid in return for Pyongyang taking steps to suspend its nuclear programmes, but the deal was proclaimed dead in 2008 by the North and the United States.
The United States and South Korea demand the North take steps agreed in the 2005 deal as a precondition to more talks, but Pyongyang and Beijing, which has hosted the negotiations, have since sought an unconditional resumption.
Isolated and poverty-stricken North Korea, which regularly threatens to destroy the United States and South Korea in a sea of flames, defends its nuclear programme as a "treasured sword"to counter what it sees as US-led hostility.