Germany is worried by signs of weakening in the network of multilateral organisations and agreements designed to foster international cooperation, Chancellor Angela Merkel said on Monday.

Merkel blamed the fraying of the multilateral order on a "double transition" - the gradual fading of the direct memory of searing global conflict and the sheer pace and scale of technological change.

"The people who experienced World War Two, the last true global catastrophe, are dying out and are no longer there as eyewitnesses," she told a conference in Berlin.

"They learned from that terrible experience not to embed emnity but that you had to try and build friendships with each other," said Merkel, Europe's longest serving leader.

At the same time, emerging digital technologies are transforming the global economy in a way comparable only to the invention of the printed book centuries ago, creating disruption that no individual state could hope to manage on its own.

"International agreements and institutions are being weakened. This is worrying, since our multilateral global order comes from the lessons we learned from the terrible world wars of the last century," she said.

The same went for global trade, where she warned against protectionist instincts that might endanger open markets.

Regretting the failure to seal a deal on the trans-Atlantic TTIP trade partnership, Merkel stressed Europe's continued willingness to discuss the trade relationship with the United States, but warned against a confrontational approach.

"We are happy to negotiate, but it mustn't be under a sword of Damocles," she said, in an apparent reference to US President Donald Trump's more belligerent stance on world trade.

Merkel said she still hoped there would be no need for the European Union to implement retaliatory measures in its trade dispute with the United States.

Trump imposed a 25 percent tariff on steel imports and a 10 percent tariff on aluminium in March but the EU has been granted exemptions until June 1.