HONG KONG • China is not obliged to help defend North Korea as the latter's development of nuclear weapons has breached a mutual defence pact, Chinese diplomatic and military observers told the South China Morning Post (SCMP).

China and North Korea signed a mutual aid and cooperation treaty in 1961 as they sought to mount a united front against Western powers. Renewed in 1981 and 2001, the treaty is valid until 2021.

The Sino-North Korean Mutual Aid and Cooperation Friendship Treaty stipulates that one country must immediately take military and all other necessary measures to oppose any country or coalition of countries that might attack either nation. But the treaty also says that both nations should safeguard peace and security.

Observers told the SCMP that North Korea's development of nuclear weapons in violation of the United Nations treaty on non-proliferation could amount to a breach of the pact. This means that Beijing is not obliged to help defend North Korea from a military attack, they told the paper.

"It is hard to say how China would assist North Korea militarily in case of war, since North Korea is developing nuclear weapons, an act that might have already breached the treaty between the two nations," said retired Chinese naval colonel Li Jie.

In the case of Pyongyang initiating an attack, China would not be obliged to get involved, said Professor Cai Jian of Fudan University.

Mr Antony Wong Dong, a Macau- based military analyst, said that when the treaty was last renewed, China warned North Korea that it must take responsibility for its own behaviour.

"There won't be a second Korean war," Mr Wong told the SCMP.

The Global Times, which is published by the Communist Party's People's Daily, said in an editorial that the best option for North Korea and its leader Kim Jong Un was for the country to give up its nuclear programme, and China would protect North Korea if it did, reported Reuters.

"As soon as North Korea complies with China's declared advice and suspends nuclear activities... China will actively work to protect the security of a denuclearised North Korean nation and regime," said the Global Times.