US Secretary of State John Kerry warned Monday that "

"Anxieties are building up in a lot of places and they're manifesting themselves in the politics day to day all over the world," said the top American diplomat.

Kerry was speaking in Berlin at the start of his European farewell tour, six weeks before he and the rest of President Barack Obama's administration hand over to the Trump team on January 20.

The populist billionaire has vowed to rip up key diplomatic achievements reached under Kerry -- from the Iran nuclear deal to a trans-Pacific trade pact -- and is now looking for a successor at the helm of the State Department.

Kerry did not mention Trump but alluded to the US election and pointed to other political upheavals: Brexit, Sunday's Italian referendum that cost Prime Minister Matteo Renzi his job, and the Austrian presidential vote where a far-right candidate came in a strong second.

"You see it in the anxieties of Italy voiced yesterday or the anxieties of Austria, where the election came out a different way but the anxieties were there," said Kerry.

"You see it in Brexit," he said on Britain's shock vote in June to leave the EU.

But Kerry added confidently, as he accepted the German Cross of Merit from his counterpart Frank-Walter Steinmeier, that this was no time to "put your head in the sand" and added: "We are gonna to be ok."

For seven decades "our alliance has helped move this continent and our planet toward greater peace, security, and freedom", he said.

This had been true "regardless of partisan political affiliations" on either side, "and that cannot, and must never, change"

'A thousand miles away'

Kerry from Tuesday joins a NATO foreign ministers' meeting in Brussels which, a US diplomat said, aims to help "strengthen NATO's security .. and to strengthen NATO-EU cooperation".

Yet partners will also seek clarity after Trump has suggested Washington might think twice about coming to the rescue of a NATO ally under threat if it had not paid its dues to the alliance.

On Wednesday Kerry will travel to the northern German city of Hamburg for a foreign ministers' meeting of the 57-member Organization for Security and Cooperation in Europe.

Also there will be Russian Foreign Minister Sergei Lavrov, Kerry's counterpart amid tensions over the Ukraine conflict and the Syrian war, where Moscow backs the regime of President Bashar al-Assad.

Meanwhile, back in the United States, Trump's team was searching for a candidate to replace Kerry, as the president-elect has been firing off diplomatic broadsides on Twitter, including one accusing China of military expansionism and currency manipulation.

Whoever becomes the nominee to succeed Kerry, said Trump's senior aide Kellyanne Conway, must be ready to "implement and adhere to the president-elect's America First foreign policy, if you will, his view of the world".

Kerry at the weekend said he was "working to stay a thousand miles away from the Trump transition and the process".

Asked whether the Trump team had sought State Department input so far as it has made contact with foreign leaders, Kerry said "we have not been contacted before any of these conversations".

In Europe, some fear the worst if Trump, as promised, steers the superpower toward an isolationist nationalism.

Germany's former foreign minister Joschka Fischer wrote Monday that "Europe is far too weak and divided to stand in for the US strategically, and, without US leadership, the West cannot survive".

Steinmeier, in his speech, sent a direct a message to the Trump team: "We want to sit down and have a conversation. It's important, and it's urgent."