German Foreign Minister Heiko Maas voiced criticism of the UK's plans to increase its nuclear arsenal in an exclusive interview with DW on Thursday.

"We don't want nuclear weapons arsenals to grow. If you don't want that to happen, you can't expand them," Maas said when he sat down with DW's Chief International Editor Richard Walker in Berlin.

DW then asked the foreign minister what he thought of British Prime Minister Boris Johnson's announcement this Tuesday that his government would lift the cap on the number of Trident warheads in the United Kingdom's nuclear stockpiles for the first time in more than 30 years. 

Maas replied that the German government: "is of the opinion that there are already too many nuclear warheads in the world, not too few. That is also why we don't want nuclear arsenals to grow."

The Social Democrat added: "The past has shown that if one side has more nuclear weapons, the other side will try to catch up. And that is the disastrous arms race we have been in for decades."

The UK deploys its Trident missiles in four submarines, one of which continuously cruises the seas in order to maintain the ability to counterstrike in the event of nuclear attack. The decision will raise the ceiling on the number of missiles in the UK's nuclear stockpile — from the current cap of 225 to 260 warheads — and more than reverses previous plans to cut the cap to 180 by the middle of this decade.

Maas says binding international treaties are key

When asked directly if he considered the UK's decision to be a mistake, Maas reiterated that Germany wants to see arsenals shrink, replying: "If that is what you want, then you can't expand them."

Maas stressed the importance of international treaties in that regard, saying people must be able to count on them limiting arsenals and prohibiting their expansion.

Still, he acknowledged that such a situation could only works if all sides followed the rules.

Without international rules, "we'll always see that individual countries feel as if they need to acquire new weapons systems to maintain deterrence. Unfortunately, that is the situation we currently find ourselves in," he said.

US using 'clear language' towards Russia

Maas was also asked about US President Joe Biden's recent comments that appeared to imply Biden believes Russian President Vladimir Putin is "a killer."

He refrained from addressing that specific comment but noted, "there is very clear language in the United States with regard to Russian activities, for example in Syria, but also when it comes to influencing elections in third countries."

The German diplomat stressed the pragmatism tied to that direct approach: "I believe it's an important signal that American foreign policy is clear on the one hand when it comes to human rights and freedoms, but also that it wants to be in a position to keep the window for dialogue with Moscow open when it comes to major challenges such as disarmament and climate change," Maas said.

Crimea annexation 'clear violation of international law'

Speaking almost exactly seven years after Russia annexed Crimea from Ukraine, Maas said the act "was and is a clear violation of international law," saying that Germany and many allies' position remained that this should be undone. He said it was "not an issue that can be solved militarily, but we will continue to make this expectation clear to Russia." 

He said that Russia itself might had an interest in normalizing ties with Europe once again, years after its exclusion from what now is once again the G7. An important step towards improving ties would be "finding a solution to the conflict in eastern Ukraine."

Asked whether he truly believed Crimea would ever become part of Ukraine again, Maas said: "That is our position. I am aware that it could prove an extraordinarily difficult path." 

Lukashenko 'trampling on our democratic values'

Maas also discussed the EU sanctions against Belarus after last year's highly contested elections and the subsequent crackdown against opposition protests and politicians. Despite the EU struggling to react as swiftly as individual nations like the US when imposing sanctions, Maas defended acting on a European rather than a unilateral level. 

"We also have to make sure that sanctions affect the right people in cases like these and do not hit civil society as a whole," Maas said. "So we must keep the economic consequences of such steps in mind. And that's why in the case of Belarus we decided to target those responsible. Not just [President Alexander] Lukashenko, but his entire apparatus." 

Asked how he viewed the man often dubbed 'Europe's last dictator', Maas said: "He is clinging on to power by dictatorial means and is trampling our democratic values underfoot."

DW's Richard Walker and Rosalia Romaniec contributed to the reporting.

Correction: This article was revised on March 19 to more accurately reflect the changes  to the ceiling on the maximum number of missiles in the UK's nuclear stockpile.