Shafiah Muhibat – Don't let the polite headlines fool you. When Timor-Leste was welcomed as the 11th member of the Association of Southeast Asian Nations (ASEAN) at the 47th Summit in Kuala Lumpur, the fanfare obscured one of the summit's most important actions.
While headlines rightly focus on the completion of the 'ASEAN family' and the resultant economic opportunities for Dili, the true strategic move was Timor-Leste's official deposit of its Instrument of Accession to the Southeast Asia Nuclear Weapon-Free Zone (SEANWFZ) Treaty on 25 October 2025. Critics have long dismissed SEANWFZ, but by focusing solely on its military limitations, they miss its political substance.
By making this commitment immediately, the newest and smallest ASEAN member has delivered a foundational diplomatic signal, reasserting the bloc's identity as escalating geopolitical pressures threaten to fragment it. Timor-Leste is not just completing the map. It is rescuing ASEAN's most defining principle: neutrality.
The context of this accession is critical. ASEAN is caught in the precarious geopolitical vice of rising US – China rivalry. Member states are under immense pressure to align, particularly on security matters relating to the South China Sea and the broader Indo-Pacific, which threatens to erode the bloc's hard-won 'centrality'. This tension has left ASEAN struggling for consensus, often leading to divided statements and diplomatic gridlock.
Against this challenging backdrop, many strategists view the SEANWFZ Treaty with scepticism. Critics dismiss it as an artefact of the post-Cold War era that lacks real teeth. They argue that for the treaty to be truly effective, the five recognised Nuclear Weapon States – the United States, China, Russia, France and the United Kingdom – must sign and ratify its protocol. All five states have consistently refused to take this step. In this view, Timor-Leste's signing is a symbolic gesture with no practical security impact.
But this cynicism misses the profound political significance of Timor-Leste's move. In today's volatile environment, the SEANWFZ Treaty is not a military shield but a crucial political and normative instrument that defines the region's commitment to peace. Its value lies in its existence as a normative barrier – a collective declaration that Southeast Asia will not be the theatre for a nuclear arms race.
Crucially, this move remains consistent with Timor-Leste's established disarmament credentials. For a nation forged in the crucible of conflict and whose sovereignty remains its highest political priority, the decision to accede to the SEANWFZ is consistent with its long-standing foreign policy of active non-alignment. Indeed, Dili had already demonstrated this commitment in 2022 by acceding to the global Treaty on the Prohibition of Nuclear Weapons.
By prioritising this regional treaty now, Dili signals scepticism towards external military guarantees and alignment, choosing instead to contribute to a regional architecture of peace.
The treaty's strategic significance lies in geographical closure. Since its inception in 1995, the SEANWFZ Treaty had been legally incomplete. The territory of Timor-Leste represented a conspicuous geographical and political loophole in the map of Southeast Asia's non-nuclear commitment. This technical ambiguity could, in the most extreme hypothetical scenarios, have been cited or exploited by outside powers seeking to disregard the zone's integrity.
Before 25 October 2025, the zone was politically powerful but geographically fragmented. With the accession of Timor-Leste, Southeast Asia's entire landmass and contiguous maritime space is formally and legally covered by the SEANWFZ Treaty. This achievement gives ASEAN a powerful and unified foundation in multilateral forums, significantly reducing any residual ambiguity regarding the zone's physical boundaries.
By making one of its first acts of full ASEAN membership the accession to the SEANWFZ Treaty, Timor-Leste affirmed its commitment to regional security through non-alignment and disarmament. This was an essential political move. ASEAN relies on international law and diplomatic consensus for its survival, not hard power. Timor-Leste is using its entry to re-legitimise ASEAN's security ambition and act as a new anchor for neutrality, pushing back against the narratives that seek to militarise Southeast Asian waters.
The power of this commitment is amplified when contrasted with the hesitation and division of some older ASEAN members on geopolitical issues. Timor-Leste, as a nation born from conflict and founded on democratic principles, prioritises the architecture of peace. Its uncompromised adherence to a major legal commitment immediately upon entry offers welcome stability.
At the same time, accession to the treaty is particularly notable for the ASEAN Political-Security Community. While the regional body struggles to find a unified position and enforce the political commitment of the Five-Point Consensus on Myanmar, the newest member demonstrates the immediate political will to fulfil a major international legal obligation under SEANWFZ.
This draws a stark contrast between the willingness to commit to a formal framework and the inability of some long-standing members to honour their political pledges.
While the institutional and administrative capacity of Timor-Leste still lags, a challenge that requires technical support through the Initiative for ASEAN Integration, its political principle is undeniable. With the uncompromised voice of its newest member now at the table, ASEAN has been strategically reinforced, offering a much-needed foundation to reassert its defining ideal of neutrality. This resolve, however, marks only the start of the difficult journey to restore consensus and centrality amid intensifying great power rivalry.
[Shafiah F Muhibat is Deputy Executive Director for Research at the Centre for Strategic and International Studies, Indonesia.]
Source: https://eastasiaforum.org/2025/11/25/timor-leste-steps-up-as-aseans-new-neutrality-anchor