Timor-Leste ratifies CTBT, unversalising Treaty in South-East Asia

The Democratic Republic of Timor-Leste has deposited its instrument of ratification for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) with the United Nations Secretary-General, becoming the 174th State to ratify the Treaty.

This is the fourth ratification during the CTBT’s 25th anniversary year, strengthening the international norm against nuclear testing and building further momentum towards global adherence to the Treaty and its entry into force.

Timor-Leste’s ratification universalises the CTBT in South-East Asia, unifying the region on a key nuclear disarmament and non-proliferation issue.

It also aligns the country with the policy of all ASEAN Member States, which have already ratified the Treaty.

The event was marked on August 1 in a ceremony at United Nations Headquarters in New York on the margins of the 10th Nuclear Non-Proliferation Treaty Review Conference (NPT RevCon), and attended by Karlito Nunes, Permanent Representative of Timor-Leste to the UN, and Andrei Kolomoets, Acting Chief, Treaty Section of the UN Office of Legal Affairs.

“The Democratic Republic of Timor-Leste is proud to ratify the CTBT to help prevent nuclear proliferation and promote disarmament for peace and stability. We look forward to working with the CTBTO to explore the International Monitoring System's civil and scientific benefits,” said Timor Leste’s Minister of Foreign Affairs and Cooperation, Adaljiza Albertina Xavier Reis Magno.

Robert Floyd, Executive Secretary of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) applauded the decision: “Timor-Leste's ratification of the CTBT reaffirms the region's resolute commitment to nuclear disarmament and non-proliferation, and peace. This is a significant accomplishment, as we celebrate the twenty-fifth anniversary year of the Treaty. I look forward to strengthening our cooperation through capacity building and training opportunities to ensure Timor-Leste reaps the full benefits of membership.”

He further stated: “Let me also thank Timor-Leste for ratifying the CTBT as the world gathers at the United Nations headquarters for the 10th NPT RevCon, a demonstration of the country’s commitment to a world free of nuclear tests. The CTBT and its verification regime deliver on the NPT’s aspiration of ending nuclear tests.”

The CTBTO head made an official visit to Timor-Leste’s capital, Dili, in March 2022.

During his trip, Floyd met with officials who played a key role in the country’s ratification process, including Prime Minister Taur Matan Ruak, Minister of Foreign Affairs and Cooperation, Adaljiza Magno, and Minister of the Presidency of the Council of Ministers, Fidelis Leite Magalhães and President of Commission B, José Agostinho Sequeira Somotxo.

In the course of the regional visit, CTBTO’s Executive Secretary also had the occasion to meet with Aniceto Longuinhos Guterres Lopes, President of the National Parliament of Timor-Leste on the sidelines of the 144th Inter-Parliamentary Union Assembly (IPU) in Indonesia, paving the way for further dialogue.

"Attainment of a world free of nuclear weapons will not be possible without an in force CTBT… There can be no excuses to continue postponing this shared goal,” said Izumi Nakamitsu, UN Under-Secretary-General and High Representative for Disarmament Affairs.


The CTBT bans all nuclear explosions everywhere, by everyone, and for all time. Adherence to the Treaty is nearly universal, with 186 signatory states and 174 ratifying states. However, to enter into force, the Treaty must be ratified by all 44 States listed in its Annex 2, for which eight ratifications are still required.

The CTBTO has established an International Monitoring System (IMS) to ensure that no nuclear explosion goes undetected. Currently, 303 certified facilities – of a total of 337 when complete – are operating around the world. The data collected by the IMS can also be used for a wealth of civil and scientific purposes, including disaster mitigation measures such as tsunami warnings and the tracking of radioactive releases from a nuclear accident.

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