António Costa said after being received by the British Prime Minister, Boris Johnson, at Downing Street in London, in a meeting that lasted about 45 minutes and also attended by the Portuguese Foreign Minister, João Gomes Cravinho.
"This agreement will be key to relaunching the oldest alliance that exists in the world after Brexit. It is one of the first that member states have signed and is perhaps the one that covers more topics, from the areas of defence, research, through investment, trade, to technologies, digital transition and renewable energy," the Portuguese leader told journalists.
"These are challenges we are facing and we have to respond to them together. The fact that we have such a strong scientific community here in the UK helps a lot to build bridges between our scientific and university institutions," he said.
António Costa also stressed that the UK "has been investing more and more in Portugal, with British companies benefiting from the advantages of Brexit in the UK and the advantages of remaining in the European Union by investing in Portugal".
"They have been investing mainly in the area of technologies," he added.