The Danish prime minister said Europe must “stand together” in the face of changing relations with the US during a tour of Berlin, Paris and Brussels to shore up support amid Donald Trump’s threats over Greenland.

After weeks in the spotlight over the US president’s plan to take over the autonomous Danish territory, and days after a reportedly “horrendous” call with Trump, Mette Frederiksen went on the whistle-stop tour in an attempted show of unity.

After meeting the German chancellor, Olaf Scholz, who said that “borders must not be moved by force”, Frederiksen said: “I want to ensure that all of Europe stands together. Not only in connection with the kingdom of Denmark but also more broadly.”

Frederiksen, who also met the French president, Emmanuel Macron, added: “Everyone in Europe can see that it will be a different collaboration with the USA now.

“At least these are the tones we hear from Washington in relation to trade and economic cooperation. What the consequences of that are, we don’t know yet.”

Speaking ahead of her final stop of the day in Brussels, where she planned to meet Nato secretary general Mark Rutte, she also said she was working “very, very hard right now” to look after Denmark’s interests.

“Regardless of what happens in the USA, Europe must stand stronger in its own right,” the Social Democrat leader added.

Trump has refused to rule out using military force to take the Arctic island, part of the kingdom of Denmark, which continues to control Greenland’s foreign policy and defence.

He appeared to double down on his geopolitical ambitions over the weekend, declaring: “I think we’re going to have [Greenland].” He was reported to have threatened Denmark with tariffs.

Asked if she would speak to Trump again, Frederiksen said she would not “go into concrete calendar gymnastics” but added: “The dialogue we have with the Americans takes place on several different channels and levels.”

At their joint press conference in Berlin on Tuesday, neither Scholz nor Frederiksen mentioned Trump or Greenland, but it seemed clear the issue was on their minds.

After speaking about Russia’s 2022 full-scale invasion of Ukraine and how “inviolability of borders is a fundamental principle of international law”, Scholz said: “The principle must apply to everyone. I made that clear again from this point a few days ago. Borders must not be moved by force.”

Switching to English, he added: “To whom it may concern.”

Frederiksen said Europe was facing a “more uncertain reality” that called for greater cooperation.

“We need a stronger and more resolute Europe standing increasingly in its own right, capable of defending and promoting Europe and the European interests,” she said. “We have to take more responsibility for our own security.”

EU leaders will hold their first summit dedicated to defence next Monday, to discuss funding and new military capabilities. Defence has risen up the agenda since Russia’s invasion of Ukraine, but the return of Trump, who has previously said he would encourage Russia to attack Nato allies considered not to be paying their fair share, has made the issue more urgent.

So far most EU leaders have refrained from commenting directly on Trump’s incendiary comments about Greenland, which sources said was a deliberate strategy. A senior EU official said it had been decided “not to go for a tit-for-tat because it is not seen as helpful”.

The official said at this stage “instead of escalating it is probably more useful” to let Denmark continue to represent itself, “but we are totally and fully supportive of them”.

They added: “One of the challenges of the new administration will be the united reply [from the EU] but also to know when to reply, or are we just escalating a confrontation?”

The previous 24 hours had brought a raft of announcements – including on defence and tackling racism against Greenlandic people in Denmark – by the Danish government, aimed at appeasing Greenlanders and the US.

It has been a challenging January for Frederiksen, as Denmark has been singled out by the US and publicly threatened not just with tariffs but potential military intervention over Greenland.

On Sunday night, amid leaks of her reportedly “horrendous” 45-minute call with the US president, she put on a show of Nordic unity by sharing a photo on social media of a cosy-looking dinner at a kitchen table with the Norwegian prime minister, Jonas Gahr Støre, the Swedish prime minister, Ulf Kristersson, and the Finnish president, Alexander Stubb.

Among the plans announced by Denmark this week include a 14.6bn krone (£1.65bn, $2bn) agreement with Greenland and the Faroe Islands to “improve surveillance and sovereignty assertion in the regions”.

The plans include three new Arctic ships that can carry helicopters and drones, two long-range drones that can acquire detailed images over long distances, and improved “satellite capacity” to monitor the Arctic and northern Atlantic.

Trump has previously ridiculed Denmark’s defence plans for Greenland. By boosting spending, Copenhagen will hope to demonstrate that it is capable of defending Greenland.

The Danish government said the agreement would also enable more young people in Greenland – which has a population of 57,000 – to gain skills “to take responsibility for preparedness and asserting sovereignty”.

Another agreement between the parties to strengthen deterrence and defence is expected later in 2025.

The Danish government has also announced a plan aimed at tackling racism against Greenlanders. It has said the initiative, which has been years in the making, will allocate an additional 35m DKK over four years.

The Inuit Circumpolar Council, the body that represents all Inuit from Alaska, Canada, Chukotka and Greenland, said the last few weeks had shown how important the Arctic was to the international agenda. However, it warned, there was “no such thing as the better coloniser”.

“We do not wish to debate which state is better or worse to live in or is a better or worse coloniser,” it said in a statement.

“Rather we want to debate how we improve Inuit lives, livelihoods, wellbeing and self-determination across all our regions.”