SYDNEY • Asean and Australia yesterday expressed "grave concerns" about escalating tensions caused by North Korea's nuclear and ballistic missile programmes, saying they threaten regional and global peace and security.

In a joint declaration after a special leaders' summit, both sides reiterated their support for the "complete, verifiable and irreversible denuclearisation of the Korean peninsula in a peaceful manner as well as initiatives towards establishing peace in the Korean peninsula".

Singapore Prime Minister Lee Hsien Loong said Asean is "cautiously encouraged" by recent reports of its commitment to denuclearisation and its pledge to refrain from further nuclear and missile tests during this period, as well as by plans for US President Donald Trump and North Korean leader Kim Jong Un to meet.

"We hope that these recent steps will contribute towards lasting peace and stability," he said at a press conference with Australian Prime Minister Malcolm Turnbull.

Pyongyang has pursued its weapons programmes in defiance of UN Security Council sanctions and boasted of plans to develop a missile that could hit the US mainland, saying they are a necessary deterrent against a perceived threat by the US, which stations 28,500 troops in South Korea.

"We strongly urge the DPRK to immediately and fully comply with its obligations under all relevant United Nations Security Council Resolutions," the declaration said, using the initials for North Korea's official name. "We welcome efforts to improve inter-Korea relations. We also welcome Asean's readiness to play a constructive role in contributing to peace and stability in the Korean peninsula," the statement added.

Tensions have eased in recent weeks, coinciding with the North's participation in the Winter Olympics in the South, and Mr Trump accepting Mr Kim's invitation to meet.