The United States and its Western allies have insisted they will be united in responding strongly to any Russian incursion into Ukraine before talks between Washington and Moscow’s top diplomats over the crisis.

US Secretary of State Antony Blinken on Thursday said any “new acts of aggression” from Moscow towards its neighbour would be met with a “swift, severe, united response” from the White House and its partners.

Blinken’s remarks to reporters came after he held talks in Berlin with officials from the so-called transatlantic quad group – made up of the US, Germany, France and the United Kingdom – as part of a whistle-stop diplomatic tour to Europe aimed at finding a way to defuse tensions with the Kremlin.

On Friday he will meet Russian Foreign Minister Sergey Lavrov in Geneva, with the latter expected to press for Russia’s sweeping wishlist of security demands to be met to ensure peace.

Eyeing those talks, Washington’s European allies also stressed on Thursday that they remained in line with the US after remarks by President Joe Biden on Wednesday suggested there may be divisions between Western leaders over how to react in the event of an attack.

Ursula von der Leyen, chief of the European Union’s executive arm, said the bloc would respond to any Russian incursion into Ukraine “with massive economic and financial sanctions”.

“The transatlantic community stands firm in this,” she said.

Meanwhile, German Foreign Minister Annalena Baerbock demanded Moscow take urgent “steps towards de-escalation”, cautioning any “further aggressive behaviour or aggression” from Russia would result in “serious consequences”.

“This is nothing less than a question of maintaining peace in Europe. For us it is existential,” she told reporters at a joint news conference alongside Blinken.

‘There are no minor incursions’

The flurry of warnings came after Biden said on Wednesday that he expected Putin to launch some kind of action in Ukraine having massed tens of thousands of troops near the two countries’ shared border.

But the US leader appeared to suggest Washington and its allies could argue over the response if Moscow stopped short of an invasion.

“My guess is he will move in … he has to do something,” Biden told reporters at the White House.

“What you’re going to see is that Russia will be held accountable if it invades. And it 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 added, before warning that a full-scale invasion would signal “disaster” for Moscow.

On Thursday, the US president sought to clarify his remarks, warning of “severe and coordinated” sanctions against Russia if it moves troops into Ukraine.

“If any, any assembled Russian units move across the Ukrainian border, that is an invasion,” Biden told reporters at the White House.

Biden initial comments drew a rebuke from the Kremlin and also appeared to anger Ukrainian President Volodymyr Zelenskyy, who issued an unusually blunt public riposte towards Kyiv’s most powerful ally.

“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 tweeted on Thursday, a day after he met Blinken in the Ukrainian capital.

Nord Stream 2 threat

Repeated rounds of economic sanctions on Russia since it annexed Ukraine’s Crimean Peninsula and supported a separatist revolt in the country’s east in 2014 appear to have had a scant effect on the Kremlin’s approach towards its neighbour so far.

Moscow, Europe’s main energy supplier, has long-calculated that the West would stop short of steps serious enough to interfere with gas exports.

But US and European officials say there are still strong financial measures that have not been tried. Germany signalled on Tuesday that it could halt Nord Stream 2, a new gas pipeline from Russia that skirts Ukraine, if Moscow invades again.

Russia denies it is planning an attack, insisting it has the right to move its troops on its own territory as it sees fit and blaming the US and NATO for the deteriorating security situation in the region instead.

But Moscow has also warned it could take unspecified military action unless its security demands are met.

Among Moscow’s proposals, many of which are considered non-starters by the West, is a call for the Washington-led NATO military alliance to end military activity in Eastern Europe and Ukraine and never embrace the former Soviet republic as a new member.