“The US could leave NATO if we are not treated fairly.”
– Donald Trump, 8 December 2024.

US President elect Donald Trump has once again caused a stir by declaring the possibility of a US withdrawal from NATO. This statement, although controversial, is nothing new in the political rhetoric of Trump, who had already raised doubts about the role and sustainability of the Alliance during his presidency. But what does this statement really mean and what implications might it have for international politics? Let’s delve deeper.

What did Trump say and why?

Trump accuses NATO of being an ‘unbalanced’ organisation in terms of financial contributions, claiming that the US, as the main funder, does not receive equal treatment compared to other members. This rhetoric reflects a view that Washington bears the main burden of the Alliance’s military expenditure, while many European allies contribute only a small part.

Already during his first presidential term , Trump had threatened to withdraw the US from NATO unless the allies increased their contributions to reach the 2 per cent of GDP target for military spending, set during the 2014 NATO summit. Although some progress has been made, Trump believes that many countries, including Germany, Italy and Spain, are not fully meeting their commitments.

Why does the US support NATO?

NATO (North Atlantic Treaty Organisation) was founded in 1949 to ensure the collective security of its members against common threats, notably the Soviet Union during the Cold War. The United States was among the main promoters of the Alliance, seeing it as a pillar for European stability and a tool to contain rival influences, such as those of Russia and China.

However, in the post-Cold War world, many American politicians, including Trump, believe that NATO no longer meets modern security needs, such as countering international terrorism and competing economically and technologically with China. Moreover, Trump has often pointed out that US military spending represents a disproportionate share compared to other members, fuelling the debate on the Alliance’s effectiveness.

The implications of an American exit from NATO

An eventual US withdrawal from NATO would be unprecedented and have significant consequences:

• Weakening European security: the US is the Alliance’s main military force and provides crucial resources such as strategic bases, missile defence systems and global projection capabilities. Without their support, Europe could find itself vulnerable to external threats, particularly from Russia.
• Uncertain future of the Alliance: An American exit could lead other members to reconsider the value of NATO and explore alternatives, such as greater defensive integration in the European Union.
• Global realignments: An American withdrawal could strengthen the positions of rival powers, such as Russia and China, which have long sought to undermine transatlantic unity.

Would Trump have the authority to do so?

Whether a president can unilaterally withdraw the United States from NATO is a subject of legal debate. Article 13 of the North Atlantic Treaty provides that a member may withdraw by notifying the US government, which in turn informs the other members; the withdrawal becomes effective after one year.

However, the US Constitution does not clearly state whether the power to abandon international treaties rests solely with the president or requires congressional approval. In 2023, Congress passed a law prohibiting the president from unilaterally withdrawing from NATO without the consent of a qualified majority of the Senate or an act of Congress. Consequently, such a decision by Trump could face significant legal challenges.

NATO countries’ military expenditure

To better understand Trump’s criticism, it is useful to analyse the data on NATO members’ military spending, both in absolute terms and as a percentage of GDP.

According to the Stockholm International Peace Research Institute‘s (SIPRI) 2024 report, the United States spent about USD 916 billion in 2023, accounting for just under 70 per cent of total Alliance spending. In comparison, the European allies and Canada spent a total of just over $440 billion (more precisely, $425 billion for the countries surveyed in the SIPRI 2024 report, plus an estimated $15-20 billion for smaller countries).

Here is a table showing the ratio of military expenditure to GDP for each of the major NATO members in 2024:

Military expenditure as a percentage of NATO members’ GDP (2024)

Source: Data based on NATO 2024 reports and estimates published by the Stockholm International Peace Research Institute (SIPRI).

Conclusion

Trump’s statements on leaving NATO are a wake-up call for the Alliance and Europe, which face growing challenges to their unity and relevance. Although an American withdrawal seems unlikely in the short term, Trump’s insistence raises fundamental questions about the future of transatlantic cooperation. In an increasingly fragmented global context, NATO’s ‘European shore’ may have to rethink its role and priorities in order to remain relevant and ensure collective security.