During the Trump presidency, America was fiercely hostile to any independent EU military arguing this would undermine NATO. America, Canada and Norway have all agreed to join 25 EU member states in the Permanent Structured Cooperation (Pesco).
This initiative is designed to boost European infrastructure that can be used by the military.
In was launched in 2017 as one of 46 new EU military projects.
In 2019 Donald Trump’s administration strongly criticised the programme sparking Transatlantic tensions.
Pesco, which is currently being led by the Netherlands, will ensure EU members are able to quickly deploy forces across the bloc to challenge any outside incursion.
This would include being able to swiftly transfer troops to the Russian border should Putin threaten any of the Baltic States.
In a statement Dutch defence minister Ank Bijleveld welcomed the move.
He said: “We are very pleased that tomorrow we expect a positive decision to welcome three important NATO countries to this EU project.
“I will send the official invitation letters soon.
The source also insisted cross-border troop authorisations within the bloc should take a maximum of five days.
The American decision to join was also saluted by João Gomes Cravinho, the Portuguese defence minister.
Portugal currently holds the Council of the EU presidency, which rotates between member states.
He commented: “It marks an availability by the U.S administration to work with Pesco.
“It’s very positive that the U.S should be joining this, rather than saying that Pesco is, which we’ve heard at some points from the previous administration negative for the interests of NATO.
In January 2020 European Commission president Ursula von der Leyen said the EU must develop “credible military capabilities” during a speech to the World Economic Forum.
She argued: “We must also do more when it comes to managing crises as they develop.
“And for that, Europe also needs credible military capabilities and we have set up the building blocks of the European Defence Union. It is complementary to NATO and it is different.”
Guy Verhofstadt, formerly the European Parliament’s chief Brexit coordinator, has repeatedly called for an EU army.
Leave campaigners used the fear Britain could be drawn into a European army to argue for Brexit during the 2016 referendum campaign.