In April, US President Donald Trump directed ^[1] White House officials to identify pathways to new arms control agreements with Russia and China. If he’s looking for a big and bold new idea, here’s one: a ‘P5+4’ nuclear summit of the leaders of the nine countries that have the bomb.

The five permanent members of the UN Security Council (the ‘P5’) are the only countries recognised by the Nuclear Non-proliferation Treaty (NPT) as lawful possessors of nuclear weapons: China, France, Russia, the UK and the US. The ‘+4’ are the non-NPT nuclear-armed countries—India, Israel and Pakistan—and North Korea, the world’s only NPT defector state.

The existing architecture of nuclear arms control has served us well but is now crumbling. It was weakened first by the US exit ^[2] from the Anti-Ballistic Missile Treaty in 2002 and then the indefinite delay of the entry into force of the Comprehensive Test-Ban Treaty. More recently, the deterioration has accelerated with the Trump administration’s abandonment ^[3] of the nuclear deal with Iran, the US and Russian suspensions ^[4] of the Intermediate-Range Nuclear Forces Treaty, and the failure thus far to discuss extending New START beyond its expiry date of 2021.

There is a related problem. The NPT-centric architecture cannot accommodate the reality of four non-NPT possessor states. The architecture deficit is exacerbated by the fact that the agenda of nuclear arms control, non-proliferation and disarmament has stalled. The Korean denuclearisation-cum-peace-process has run out of steam. Last month’s meeting of the preparatory committee for the 2020 NPT review conference could not reach agreement on a common statement ^[5].

In 2017, two-thirds of the international community adopted the UN Treaty on the Prohibition of Nuclear Weapons. All nine bomb-possessing countries, and about 30 nuclear-dependent allies including Australia, mock this as empty virtue-signalling by those who don’t have the bomb. Yet nuclear powers themselves invite ridicule by insisting that the only proper forum for engaging in arms control negotiations is the Conference on Disarmament in Geneva. This farcical body has not managed to agree on its own work agenda for over 20 years.

The primary motivations behind the Nuclear Ban Treaty were heightened consciousness of elevated levels of nuclear risks and threats, exasperation at the refusal of the nuclear-armed states to engage in credible disarmament negotiations, and frustration with the fraying arms control architecture. The primary impact of the treaty ^[6] won’t be operational but normative: it attaches a moral stigma to continued possession and to doctrines of deterrence.

So the existing international machinery is no longer fit for purpose even for individual items on the nuclear agenda, let alone all of them. Summit diplomacy could be a mechanism for cutting through the Gordian knot of global gridlock.

Not all summits are successful and not all topics lend themselves well to summit diplomacy. Summits make the most difference in tackling those global problems where leadership commitment is the critical missing variable, where the chief obstacle to identifying policy convergence and reaching consensus on next steps is the lack of an appropriate forum, and where speedy resolution is essential.

The nuclear security summits convened during Barack Obama’s time as president, for example, consolidated and strengthened the disparate national, multilateral and cooperative institutions and instruments to ensure nuclear security and prevent nuclear smuggling. They were important for having clear US presidential leadership on this critical area of the nuclear challenge and elevated the issue to the level of a global leaders’ summit.

Nuclear arms control satisfies all the key criteria for a summit. Like pandemics, climate change and biodiversity, nuclear threats spill across national boundaries and defy unilateral solutions. A summit of the nine political leaders, but only them, that is appropriately structured and has been adequately prepared can focus them to do what they alone can do—make tough choices from among competing interests and priorities. Cabinet ministers have single portfolio responsibilities. Heads of state and government have to oversee the entire agenda. With broad, overarching responsibilities, leaders can weigh priorities and balance interests across competing goals, sectors, and national and international objectives.

Before a summit, leaders’ engagement catalyses officials to focus on and resolve interagency differences, jurisdictional turf battles and veto points. At the summit, leaders’ involvement makes it possible for states to bargain across issues in order to cut deals; that is, to trade apples for oranges. After the summit, their commitment to the agenda invests it with legitimacy and prioritises its implementation and can help to redirect resources even amid constrained budgetary environments.

The first thing a nuclear summit should do is reaffirm the famous 1987 declaration by US President Ronald Reagan and Soviet leader Mikhail Gorbachev: ‘a nuclear war cannot be won and must never be fought ^[7]’. If all nine leaders sign such a statement, it can be adopted as a resolution also by the UN Security Council and General Assembly. That would reverse the recent trend to normalise the discourse of possible nuclear-weapon use and, by hardening the normative boundary between nuclear and other weapons, perhaps also help to stop mission creep with respect to the roles and functions of nuclear weapons.

Other items on the agenda could include drafting a declaration, to be duly converted into a global convention, on no first use ^[8] of nuclear weapons by any country; taking nuclear weapons off high-alert launch status as a crisis stability measure (around 2,000 ^[9] nuclear warheads are currently on high alert); securing verified reductions in warhead numbers by Russia and the US, which account for over 90% of global stockpiles; and determining how best to transition from US–Russian agreements to those involving all nuclear powers. At the same time, regional rivals could explore bilateral risk-reduction arrangements on the sidelines of the global summit.

A summit-level agreement on a few important items would be a powerful stimulus to restarting stalled talks on other outstanding items like bringing the Comprehensive Nuclear-Test-Ban Treaty into force and commencing negotiations on a fissile materials cut-off treaty. Even a modestly successful summit would tell the world that the nine powers take seriously their responsibility for preserving nuclear peace. If Trump takes the initiative and assumes ownership of the summit, he would be more deserving of the Nobel Peace Prize than Obama in 2009 ^[10].