The arrival of the new U.S. president, John F. Kennedy, in office in 1961 encouraged Aiken to redouble his efforts. He searched for signs of change in the Kennedy administration. He was nevertheless guarded,  appreciating that the arms control ambitions of the United States did not necessarily or completely align with Ireland’s disarmament aspirations. He understood that progress required educating public opinion to recognize that general and complete disarmament could, given the vested interests, take generations. A step-by-step, gradualist approach therefore had to be adopted. He reiterated his philosophy of expanding areas of law, adopting a regionalist approach, and assuming a preventive orientation in a commentary on Kennedy’s article in the Bulletin of the Atomic Scientists in November 1960, which was itself based on Kennedy's campaign speech earlier that year.

New Taoiseach Seán Lemass took the unusual step of intervening in a Foreign Affairs debate in July 1959 to defend Frank Aiken’s conduct at the United Nations. Trenchant critics on the opposition benches in the Fine Gael party had berated Aiken repeatedly since 1957. Critics inside and outside of the lower house of parliament (Dáil Éireann) asserted that Ireland, “a tiny country” with limited interests, had no right to voice an opinion on global matters which was more appropriately dealt with by the “Great Powers.” Worse, Aiken’s interventions would create enemies among Irish friends worldwide, most notably in the United Sstates. The tenor of the arguments was that Ireland had no nuclear energy industry and no nuclear weapons aspirations, so such matters should be left to the nuclear powers. It is difficult to avoid the sense that elements in Irish political life appreciated that American and NATO nuclear forces informally protected the anti-communist Republic of Ireland. Lemass ended speculation that he was less of a supporter of Aiken than his predecessor, de Valera. He affirmed that Ireland had a significant contribution to make to the global commons in terms of reinforcing peace and order. Aiken was empowered to continue.

First Secretary Eoin MacWhite informed all missions of Aiken’s concerns that U.S. nuclear information agreements with selected NATO partners could impede efforts to prevent the spread of nuclear weapons. He was nonetheless reticent when it came to lodging a formal protest, having been advised by Eoin MacWhite that a strong denunciation would be counterproductive. From MacWhite’s reading no actual nuclear information would be transferred to Allied personnel after all. The agreements related specifically to information necessary for the training of Allied personnel in the employment of U.S. atomic weapons in their hosts’ territories, so Aiken recoiled from further diplomatic protests. He appreciated the need to maintain some nuance on nuclear sharing as he pursued an East-West consensus. 

The strength of NATO's feelings in favor of enhanced alliance nuclear defense and cooperation in the aftermath of the Sputnik shock was well known. The Irish were aware of the Eastern bloc’s objections to NATO nuclear sharing as a dangerous precedent that strengthened NATO’s political and security position. Moscow was especially exercised by any prospect of West German access to nuclear weapons as part of the normalization of German rearmament and progress toward reunification. Moscow opposed any semblance of Bonn’s finger on the nuclear trigger, or its troops gaining proficiency with nuclear weaponry. 

The report of Ireland’s permanent representative to the United Nations to his superior, the secretary of the Department of External Affairs, delivers his account of Aiken’s first (failed) attempt to generate support for a resolution in the Thirteenth UN Session. Recognizing the breadth and depth of opposition, he withdrew his draft resolution and instead requested a simple roll call vote in favor of the second paragraph on 31 October – a modest statement acknowledging that an expansion in the number of nuclear weapons states would be harmful to peace and increase obstacles to disarmament. The measure passed with 37 votes and no opposition, although 44 abstentions were recorded. The Soviet bloc supported the maneuver, while Western-aligned countries abstained.  

Aiken’s first step was a modest paragraph calling for the formation of a UN commission to recommend measures to the next session. However, global attentions were focused on nuclear tests and their health effects, so Aiken linked his initiative with the American-led seventeen-power resolution requesting all states to suspend testing voluntarily. Aiken proposed an amendment to that motion that included the notion of brokering an understanding between nuclear weapons powers and non-nuclear powers.  He submitted that the former voluntarily desist from supplying nuclear weapons to other countries, while non-nuclear powers reciprocated and volunteered not to develop such weapons during a test suspension. This proposed quid pro quo became a staple in the Irish resolutions subsequently and eventually be inscribed into the NPT.

Aiken’s speech invoked recognizable tropes such as a ‘geometric’ increase in nuclear powers, creating an urgent need to halt the spread. His speech was seminal in identifying themes he and international opinion would rehearse in future years. He conjured up fears about small states and revolutionary groups with a bomb acting as ‘the detonator for world-wide thermonuclear war’. Aiken was perceptive – he expected criticisms about institutionalized equality between states (nuclear “haves” and “have nots”), harms to alliances, the sufficiency of test bans, and the absence of monitoring. He sought to disprove the validity of such critiques, and these issues were worked through gradually, eventually leading to the finalization of the NPT ten years later.  

Aiken’s landmark address to the plenary of the UN General Assembly on 19 September 1958 launched his non-proliferation campaign. It is the first time he publicly identified stopping the spread of nuclear weapons as a concrete step in the collective interest to unblock the disarmament impasse, preventing a runaway arms race among the powers of the Earth. It was clearly framed as part of his wider campaign for global governance based on the rule of law rather than the threat of force. For Aiken, the challenge was stabilizing the arms race and generating trust to construct a world order based on justice and law – “to preserve a Pax Atomica while we build a Pax Mundi.” This speech was a critical departure. The widespread positive reception encouraged Aiken, persuading him to draft a formal resolution.

Aiken made an immediate impression on his arrival in the Twelfth Session of the UN General Assembly in September 1957. He adopted an impartial posture of assessing each issue on its merits and campaigning to remodel international politics around self-determination, humanitarianism, and peace. His exhortation was that only the UN had the moral authority and political legitimacy to put forward global solutions. While he did not propose nuclear disarmament measures specifically, his intent was signaled by his recommendation for a mutual drawback of foreign forces (including their nuclear weapons) in central Europe and his endorsement of a proposal to discuss the representation of China in the United Nations. The Eisenhower administration was hostile to Aiken’s course as outlined in the U.S. ambassador’s audience with Taoiseach Eamon de Valera and Aiken in Dublin on 2 October. The record underlines the Irish concerns about accidental nuclear war due to the proximity of opposing U.S. and Soviet forces in central Europe.  

Subsequent to De Gaulle's November 1967 veto of Wilson's EEC application, senior British ministers still saw the European question as having considerable importance. Shortly before his departure from the role of Foreign Secretary, George Brown reported to the Defence and Oversea Policy Committee that the ructions over Article 3 of the NPT would be "particularly awkward for us as potential members of EURATOM and the E.E.C." De Gaulle's second "Non!" only served to postpone Britain's membership of the EEC, as Edward Heath's Conservative government successfully campaigned for accession, which took place in 1973.

By the early summer of 1967, Foreign Secretary George Brown felt compelled to comment that "if the situation should arise in which there is a direct confrontation between the United States and Russians on one side—and the members of EURATOM on the other, on the issue of the acceptability of EURATOM safeguards we should have to consider our position very carefully: the whole success of our European policy might depend on the choice we made. For the present it should therefore be a major aim of our policy at Geneva to see that things do not reach such a state." This came only a week after Wilson formally launched the UK's bid to become a member of the EEC, and two days after De Gaulle cast doubt on Britain's fitness to join the community.

Two "Notes for the Record" from March 1, 1967, describe the vigorous discussions between senior UK government figures, including Harold Wilson, Foreign Secretary George Brown, Minister of State for Foreign and Commonwealth Affairs Lord Chalfont, and chief scientific adviser to the government Solly Zuckerman. Brown argued that "our posture on the matter should be distinctively European rather than one of supporting the United States against other European countries." Wilson was even more explicit, stating that "our approach should be that of a European power discussing the matter with European partners and not seeking to fight American battles." Wilson was keen to let Washington take the lead so that his government might avoid upsetting the French, as had happened with the debates over De Gaulle's 1966 withdrawal from the NATO command structure.