China has told other Asian countries that it may leave the U.N. Convention on the Law of the Sea as a countermeasure if a ruling from an international tribunal expected in the coming weeks over territorial rows in the South China Sea runs counter to the bedrock of its position, diplomatic sources said Monday.

What China cares most about in an arbitration case brought by the Philippines is a decision on the applicability of Beijing’s “nine-dash line” that ambiguously demarcates its claims to almost the entire disputed sea.

The Philippines, the most vocal critic of China’s activities in the South China Sea among claimants, filed the case with the Permanent Court of Arbitration in The Hague in 2013 in a bid to invalidate the vaguely drawn territorial line.

China thinks the worst outcome would be for the tribunal, constituted by the 1982 convention, or UNCLOS, to rule that Beijing’s claim of “historic rights” over the sea has no international legal grounds and invalidate its expansive line, according to the sources.

China has told diplomats of the Association of Southeast Asian Nations that it does not rule out withdrawing from the convention, often referred to as the constitution of the oceans, if that happens, the sources said.

Many experts believe that the ruling will not be favorable for China, which also has territorial disputes in the South China Sea with three other members of the 10-member association, namely Vietnam, Malaysia and Brunei.

China’s massive reclamation in recent years of islets and reefs in the South China Sea — a key international shipping route that is rich in fisheries resources and is also believed to hold large oil and gas deposits — and its building of military facilities on them have generated widespread concerns, not only among the claimants, which also include Taiwan.

China, which ratified UNCLOS in 1996, has said it will neither accept nor honor the upcoming ruling by the tribunal. It has criticized the Philippines for filing the case “unilaterally” and breaking their past agreement of trying to settle territorial disputes through bilateral negotiations.

China has also asserted that the court has no jurisdiction over the case.

However, the Philippines’ action has been backed by numerous countries, including the United States and Japan, which regard it as a step toward resolving disagreements and easing tensions peacefully through international law.

While China has urged nonclaimants not to meddle in territorial disputes in the South China Sea, those countries described by Beijing as “outsiders” have said they do not take sides in the feuds but have a say in opposing to any attempt to undermine rule-based order in the region.

They have put pressure on China to respect the forthcoming ruling if it wants to be a responsible major country in the international community.

China has accused the United States, not a signatory to UNCLOS, of having no right to talk about the arbitration case and argued that it is part of Washington’s attempt with its allies in the region to contain Beijing’s growing influence in the name of international law.

China’s noncompliance with the decision is likely to damage its international image, but the tribunal has no enforcement mechanism.