Merkel: Europe cannot rely on its allies anymore

"I can only say that we Europeans must really take our fate into our own hands, of course in friendship with the United States of America, in friendship with Great Britain and as good neighbours wherever that is possible also with other countries, even with Russia," Merkel said.

"The times in which we can fully count on others are somewhat over, as I have experienced in the past few days," she added.

Merkel's strong words came after US president Donald Trump failed to commit support to Nato's Article 5, which states that an attack on one member of the alliance is seen as an attack on all, and refused to endorse a global climate change accord.

The German chancellor did not mention Trump by name in the speech, but her comments highlighted frustrations with the US president, who, in Brussels, had lectured European officials on the German trade surplus, which he said hurts the US economy.

It is not the first time she expressed ideas such as these.

In January, after Trump said in an interview that Nato was "obsolete" and Brexit was a "great thing", she said that "we Europeans have our fate in our own hands."

Since then, with the election of pro-European Emmanuel Macron as French president, Merkel sees an opportunity to strengthen the French-German motor of European integration, while the UK leaves the EU.

But the chancellor's words of caution also aimed to rally support for her campaign, as she seeks a fourth term in September's general election.

She warned of Europe's loneliness on the world stage whilst in a beer tent, speaking to supporters of her Christian Democratic party's (CDU's) Bavarian sister, the CSU.

Merkel's handling of the refugee crisis created a rift between the two parties. Only a few months ago, CSU leaders even toyed with the idea of refusing to back her in the election. However, on Sunday, the CSU crowd reportedly applauded the chancellor for minutes.

The 62-year-old Merkel also aimed her comments at her Social Democrat (SPD) rival and former European Parliament president, Martin Schulz.

Schulz, whose initial momentum in the polls is falling, wants to portray himself as a bulwark against Trump's isolationism and is keenly pro-European. He has also urged for the mutualisation of debt in the EU.

Merkel took aim at Schulz with her call for a stronger Europe and sent a clear message that she remains a reliable leader in a dramatically shifting global order.