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Umbrella state hosting nuclear weapons (NATO)

Belgium observed the second Meeting of States Parties to the TPNW in November and December 2023, but stressed that its presence should not ‘be interpreted as a first step towards Belgium’s adherence to the TPNW’, as joining the Treaty would not be in line with its disarmament approach and, moreover, would be ‘incompatible with our commitments as a NATO member’. It reiterated its full support for NATO’s ‘nuclear deterrence posture’. At the same time, it expressed its interest ‘in hearing others’ viewpoints’ and its readiness ‘to look at how mutual efforts can lead to progress towards a world without nuclear weapons’.[1]

TPNW Status

TPNW Article 1(1) prohibitions: Compatibility in 2023
(a) Develop, produce, manufacture, acquire Compatible
Test Compatible
Possess or stockpile Compatible
(b) Transfer Compatible
(c) Receive transfer or control Compatible
(d) Use Compatible
Threaten to use Compatible
(e) Assist, encourage or induce Non-compatible
(f) Seek or receive assistance Compatible
(g) Allow stationing, installation, deployment Non-compatible
TPNW voting and participation
UNGA resolution on TPNW (latest vote) Voted no (2023)
Participated in 2MSP (2023) Yes (observer)
1MSP delegation size (% women) 2 (100%)
Adoption of TPNW (7 July 2017) N/A
Participated in TPNW negotiations (2017) No
Negotiation mandate (A/RES/71/258) Voted no
Other weapons of mass destruction (WMD) treaties
Party to an NWFZ No
Party to the NPT Yes (Ratified 1975)
Ratified the CTBT Yes (Ratified 1999, Annex 2 state)
Party to the BWC Yes (Ratified 1979)
Party to the CWC Yes (Ratified 1997)
IAEA safeguards and fissile material
Safeguards agreement Yes (21 Feb 1977)
TPNW Art 3(2) deadline N/A
Small Quantities Protocol No
Additional Protocol Yes
Enrichment facilities/reprocessing plants No
HEU stocks 100–1000 kg
Plutonium stocks <50 kg

Latest developments

Belgium may sign and ratify or accede to the TPNW, but will have to make changes to its policies and practices to become compliant.

At the Kleine Brogel Air Base, Belgium hosts an estimated 10–15 US B61 nuclear bombs for delivery by Belgian aircraft, as part of a NATO nuclear-sharing arrangement.2 In July 2023, Belgium rejected accusations that such arrangements are incompatible with the Non-Proliferation Treaty.3

Four former prime ministers and foreign ministers of Belgium (Willy Claes, Erik Derycke, Yves Leterme and Guy Verhofstadt) were among the signatories to an open letter in September 2020 calling on current leaders in umbrella states to 'show courage and boldness' and join the TPNW.4


  • Belgium should renounce the possession and potential use of nuclear weapons on its behalf, end the hosting of foreign nuclear weapons on its territory, and ensure that nuclear weapons do not have a role in its defence posture.

  • Belgium should comply with its existing obligation under Article VI of the NPT and pursue negotiations in good faith on nuclear disarmament.

  • Belgium should urgently adhere to the TPNW. Until it is in a position to do so, it should welcome the TPNW as a valuable component in the global disarmament and non-proliferation architecture, work with the Treaty's states parties on practical steps towards disarmament, and attend the meetings of states parties as an observer.

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