Foreign ministers from the 10-member Association of Southeast Asian Nations (ASEAN) attended the East Asia Summit on Monday with their dialogue partners from eight other nations, including the U.S., Japan, China and South Korea.

The threat of North Korea’s nuclear programme was expected to top the agenda, particularly in the wake of the United Nations Security Council over the weekend unanimously imposing sanctions on the isolated country that could slash its $3 billion annual export revenue by a third.

ASEAN has taken a stronger tone at this year’s summit than it has previously, calling for the North to comply with U.N. resolutions and make a positive contribution to regional peace, while U.S. Secretary of State, Rex Tillerson on Monday said the resolution sends a strong message that North Korea needs to understand what the world expects of it.

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Territorial disputes in the South China Sea were also expected to be discussed after Southeast Asian foreign ministers late on Sunday issued a communique that called for militarization to be avoided and noting concern about island-building.

China is sensitive to even a veiled reference by ASEAN to its seven reclaimed reefs, three of which have runways, missile batteries, radars and, according to some experts, the capability to accommodate fighter jets.