President Trump has urged all Nato member states in Europe to follow the US example and spend four per cent of GDP on defence.
Britain’s departure from the EU next year will leave France as the only nuclear power.
President Macron’s comments came after six months of intense debate and it was raised in February by Jaroslaw Kaczynski, Poland’s former prime minister and now head of its ruling party.
And German foreign policy spokesman Roderich Kiesewetter said: “If the United States no longer wants to provide this guarantee, Europe still needs nuclear protection for deterrent purposes.
“My idea is to build on the existing weapons in Great Britain and France.”
But he acknowledged that Brexit could preclude UK participation.
President Macron said: “France is ready to enter into concrete discussions with European states on the nature of reciprocal solidarity and mutual defence relations under our Treaty commitments. Europe can no longer entrust its security to the United States alone.”
President Macron did not refer to nuclear weapons but Sir Adam Thomson, of the European Leadership Network, said: “The inference may be taken.”
But if Europe has nuclear weapons, Maj Gen Tim Cross asked: “The key question is who would own the responsibility for authorising the use of nuclear weapons? It must be one person. Would it really be the president of the European Commission? Is Europe really prepared to allow a man like Jean-Claude Juncker to have this responsibility?”