US secretary of state Antony Blinken has warned there would be a “swift, severe” response from the US and its allies if Russia sends any military forces into Ukraine.

Blinken’s comments in Berlin yesterday appeared to be another effort to clear up any confusion about the position of the US and its Nato allies after president Joe Biden was heavily criticised for saying a “minor incursion” by Russia would elicit a lesser response.

“If any Russian military forces move across the Ukrainian border and commit new acts of aggression against Ukraine, that will be met with a swift, severe, united response from the US and our allies and partners,” Blinken told a news conference with his German counterpart.

Later, Blinken accused Russia of threatening the foundations of world order with its build-up of an estimated 100,000 troops near Ukraine’s border. He said Russia must face a concerted and severe global response if it invades.

The stark warning was delivered in Berlin, as Blinken prepared for a meeting today in Geneva with foreign minister Sergey Lavrov in a high-stakes bid to ease tensions.

“These are difficult issues we are facing, and resolving them won’t happen quickly,” Blinken said. “I certainly don’t expect we’ll solve them in Geneva tomorrow.”

He said Russia’s actions toward Ukraine are an attempt to subvert international norms and just the latest in a string of Moscow’s violations of numerous treaties, agreements and other commitments it has made to respect the sovereignty and territory of other countries.

“To allow Russia to violate those principles with impunity would drag us all back to a much more dangerous and unstable time, when this continent, and this city, were split in two, separated by no-man’s-lands patrolled by soldiers, with the threat of all-out war hanging heavily over everyone’s lives,” Blinken told an audience at the Berlin-Brandenburg Academy of Sciences.

“We will not treat the principles of sovereignty or territorial integrity as negotiable,” he said, adding that the situation is “a crisis with global consequences” which “requires global attention and action.”

The speech came after Blinken and top diplomats from Europe met in Berlin to project a united front to Russia over concerns that it may be planning to invade Ukraine. A day earlier, he met Ukraine’s president in Kiev to discuss the threat.

Biden said on Wednesday that he thinks Moscow will invade and warned Russian president Vladimir Putin that his country would pay a “dear price” in lives lost and a possible cut-off from the global banking system if it does.

But, Biden also prompted consternation among allies after saying that the response to a Russian invasion “depends on what it does”. “It’s one thing if it’s a minor incursion and then we end up having a fight about what to do and not do, et cetera,” he said.

Ukrainian president Volodymyr Zelensky was among those expressing concern. “We want to remind the great powers that there are no minor incursions and small nations. Just as there are no minor casualties and little grief from the loss of loved ones,” he said on Twitter.

Blinken took pains yesterday to stress that the US and its partners were united in the face of Moscow’s actions: “That unity gives us strength, a strength I might add that Russia does not and cannot match,” he said. Russia has denied it is planning an invasion and accused the West of plotting “provocations” in Ukraine.