Britain and France should lead a new 'European Nato' to take responsibility for Europe's defence without help from the United States, an ex-Nato chief has said.
Anders Fogh Rasmussen, the organisation's secretary-general from 2009 to 2014, said a new security architecture was needed after Donald Trump threatened to withdraw from Nato.
Mr Rasmussen has suggested expanding the Coalition of the Willing - an alliance of 35 countries set up to defend Ukraine in the event of a ceasefire - so it can take over Europe's conventional defence role.
He identified France and Britain as the leading members of an expanded alliance, citing their nuclear capabilities as a key factor.
At present, the coalition is headquartered in Paris, with plans to relocate to London after its first 12 months of operation.
Mr Rusmussen's comments come following President Trump's expression of 'doubts' about his commitment to Nato and Article 5 - the mutual defence clause stating that an attack on one member is an attack on all - the European pillar of Nato must be strengthened.
The coalition, including Kyiv, is currently preparing a post-war deployment intended to deter further Russian aggression against Ukraine.
However, Mr Rasmussen argued that its scope should extend beyond Ukraine to address security across the wider continent. In his proposal, Ukraine would continue to be part of this expanded alliance.
Britain and France should lead a new 'European Nato' coalition to take responsibility for Europe's defence, Anders Fogh Rasmussen has said
He described Ukraine as an 'asset' within the coalition but said whatever the outcome of possible peace negotiations, the country will still need a 'bulwark' against Russian aggression.
Speaking to the Telegraph, he said: 'That's why I think we should include Ukraine in a new European security architecture, and by that, we can strengthen Nato.'
Mr Rasmussen said the Coalition of the Willing is now necessary as he does not 'want to include hesitant countries' that belong to other alliances, like the European Union (EU).
Several European Union member states, including Austria and Ireland, maintain military neutrality, while others are seen as more sympathetic to Moscow.
Nations such as Britain, Norway and Turkey are also not member of the alliance, however, are key Nato allies.
Mr Rasmussen's comments come amid renewed debate over Europe's future security architecture, following President Trump's criticism of European Nato allies for declining to support his war in Iran.
Mr Trump previously described the coalition as a 'paper tiger' and said withdrawing from it was 'beyond reconsideration'.
This raised doubts over whether the US president would authorise military support for European allies if Article 5 were invoked.
Mr Rasmussen has suggested expanding the Coalition of the Willing following President Trump's expression of 'doubts' about his commitment to Nato and Article 5. President Trump (right) pictured with NATO's Secretary-General Mark Rutte (left)
Mr Rasmussen (pictured) also argued Europe should not be reluctant to support Mr Trump's war in Iran, suggesting it could offer to help secure the reopening of the Strait of Hormuz in exchange for a reduction in US trade tariffs
EU member states have since been considering the strength and practicality of the bloc's mutual defence clause, Article 42.7, enshrined in the Lisbon Treaty.
Yet Mr Rasmussen described the idea as 'weaker' than Article 5.
He said: 'The European Union, as such, does not have the military capabilities needed to actually implement 42.7.'
Mr Rasmussen - who previously served as Denmark's prime minister - dismissed proposals by Andrius Kubilius, the EU's defence commissioner, for a European security council as 'fluffy'.
He said the 'hard defence of Europe' requires a group of nations in the continent that are 'capable and willing' to do what is needed.
Mr Rasmussen also argued that Europe should not be reluctant to support Mr Trump's war in Iran, suggesting it could offer to help secure the reopening of the Strait of Hormuz in exchange for a reduction in US trade tariffs.
He suggested a 'transactional' approach as appropriate as that is how 'allies work together'.
He proposed Europe's approach to Mr Trump should be to say: 'We're in this together. We are willing to help you, provided that you will stay engaged in Europe, including supporting Ukraine, and we don't understand why you are imposing tariffs on your allies.'
Mr Rasmussen said the 'hard defence of Europe' requires a group of nations in the continent that are 'capable and willing' to do what is needed
However, Mr Rasmussen emphasised that new defensive coalitions would not replace Nato – but rather work alongside it with the US assuming a leadership role within the alliance.
He said that as the Coalition of the Willing might take responsibility for the conventional defence of Europe, an overarching 'nuclear umbrella' will still be provided by the US.
He added that in this event, the coalition will require the 'Supreme Allied Commander' in Europe who must be an American.