According to a statement from Portugal's Ministry of Defence, the ministers from the 'Southern Quartet' are to gather at Porto's Palácio da Bolsa, the former stock exchange, “with the objective of aligning positions on four key themes for the security and defence of the 'southern flank'".

These themes are: “The state of the Atlantic Alliance and the future outlook, NATO's model for acting the south, trans-Atlantic relations and the implementation of the Global Strategy of the European Union in security and defence matters".

The meeting comes at a time when the new US president, Donald Trump, has suggested that his administration might scale back its commitment to international organisations in which the country is a member, such as NATO or the United Nations.

Portugal's minister of defence, José Azeredo Lopes, will be welcoming his counterparts Maria Cospedal from Spain, Jean-Yves le Drian from France, and Roberta Pinotti from Italy.

This will be the third such ministerial meeting since the Toulon gathering of 12 May of 2016, from which emerged a joint letter to the NATO secretary-general and other members of the organisation in the run up to the Warsaw summit.

The Porto meeting also takes place a week after a summit in Lisbon of seven southern European countries, at which security and defence were also discussed. In a joint statement afterwards, the countries stressed their support for the EU's Global Strategy, "so that Europe can be a credible force for peace in the region, and guarantee security and well-being to its citizens."