The US acting alone has reached the limits of its power and may already have lost its role as global leader, Friedrich Merz, the German chancellor, warned Donald Trump at the opening of the Munich Security Conference.

Merz also disclosed he had held initial talks with the French president, Emmanuel Macron, over the possibility of joining France’s nuclear umbrella, underlining his call for Europe to develop a stronger self-standing security strategy.

In a speech on Friday designed to set a firm yet conciliatory tone about the future of the transatlantic partnership, Merz argued the old order had ended and in this new age of superpowers even the US was reaching the limits of going it alone.

Referring to those that warned the international rules-based order was about to be destroyed, Merz said: “I fear we must put it even more bluntly. This order, however imperfect it was even at its best, no longer exists in that form.”

Switching to English to ram home his message, Merz said: “In the era of great power rivalry, even the United States will not be powerful enough to go it alone. Dear friends, being a part of Nato is not only Europe’s competitive advantage. It is also the United States’ competitive advantage.”

“So let’s repair and revive transatlantic trust together,” he added.

The German chancellor’s speech opened the annual gathering of top global security figures including many European leaders and the US secretary of state, Marco Rubio.

At last year’s conference, held a few weeks into Trump’s second term, the US vice-president, JD Vance, stunned European leaders by lecturing them about the state of democracy and freedom of speech on the continent – a moment that set the tone for the last year.

A series of statements and moves from the Trump administration targeting allies has followed, including Trump’s threat last month to impose new tariffs on several European countries in a move to secure US control of Greenland, a semi-autonomous territory of Denmark, a Nato ally.

Merz drew most applause from an audience brimming with hostility toward US unilateralism when he directly criticised the current American administration, saying: “The culture war of the Maga movement is not ours. Freedom of speech ends here with us when that speech is directed against human dignity and the basic law. We do not believe in tariffs and protectionism, but in free trade. We stand by climate agreements and the World Health Organization.”

“In the age of great powers, our freedom is no longer a given. It is threatened,” he said, adding that “firmness and willpower will be needed to assert this freedom”. Challenging Trump’s unilateral style, Merz added: “Autocracies may have followers, democracies have partners and allies.”

At the same time, he said Europe must cast off its excessive dependence on the US, emphasising: “We won’t do that by writing off Nato.”

He also urged the US president to recognise it was still possible to exhaust Russia economically and militarily, to the point where it was willing to come to the negotiating table over Ukraine.

With Germany one of the European countries doing the most to boost its own defence spending, Merz clearly felt in a strong enough position to insist the US needed to do more to listen to European concerns about its security and the legitimacy of a sustained European pillar of Nato.

Describing the Munich conference as a seismograph for the state of US-European relations, he said the Ukraine war “had forced Europe to return from a vacation from world history. Together we have entered an era that is once again marked by power and big-power politics.”

These big powers, Merz said, “make their own rules. It is fast, harsh and often unpredictable. These powers exploit natural resources, technologies and supply chains using them as bargaining tools.”

Merz was speaking as the fourth anniversary of the Russian invasion of Ukraine approaches and one year after Vance used his speech in the same hall to criticise Europeans for not taking enough control of their own defence arrangements and ignoring the demands of their electorates.

Merz responded by saying it was crucial for the continent to change its mindset and fully exploit the “enormous” military, political, economic and technological potential of a “sovereign Europe”. Germany was striving for “partnership-based leadership” in Europe but retained no “hegemonic fantasies”.

Merz said he had begun talks with Macron about a European nuclear deterrent. This, he said, must be firmly integrated into Nato’s nuclear arsenal and would not result in some parts of Europe being more defended than others. The chancellor stated that Germany was not abandoning Nato but wanted to establish a “strong, self-sustaining pillar” within the alliance.

In his speech Macron insisted Europe must be at the table to negotiate a new arms control settlement with Russia covering ballistic missiles, deep strike capacity, defence technology and nuclear weapons.

The French president said previous arms control treaties such as the now defunct INF Treaty were negotiated only by the US and this could not be repeated if Europe was to be taken seriously as a geopolitical power.

He said initial talks about new European security architecture had already been held with the UK and Germany, but it was now time to broaden the consultations across Europe.

Macron warned a Ukrainian peace settlement required applying extra pressure, but even if an agreement was reached Europe faced the challenge of how to “coexist with an unreconstructed aggressive Russia on our borders” that has “a bloated army and a defence industry on a sugar high”.

Calling for a transparent independent European channel of communication with Russia, he said the post second world war security architecture had been “totally designed and framed during the cold war times” and needed a new articulation.

Addressing the criticisms directed at Europe last year by Vance, Macron said “Europe has been vilified … as a repressive continent where speech is not free and where alternative facts cannot claim the same right of citizenship as truth itself – that outdated and cumbersome concept.”