Olaf Scholz, Germany’s new chancellor, warned Russia that it would face a “high price” if it attacked Ukraine, as he promised vowed a united western response to a build-up of troops on the Ukrainian-Russian border.
In his first speech to the German parliament since taking office, Mr Scholz insisted he still wanted “constructive dialogue” in order to ease tensions.
Western capitals have threatened Russia with sanctions over its troop build-up on Ukraine's border.
European Commission chief Ursula von der Leyen said that any further Russian aggression "may take the form of a robust scaling up and expansion of these existing sanctions".
"And of course, we are ready to take additional unprecedented measures with serious consequences for Russia. But above all, I call on Russia to de-escalate, to pursue diplomatic channels and to abide by its international commitments. Conflicts must be solved peacefully," she told the European Parliament.
She insisted the EU wanted good relations with Russia, but added: "Whether this is possible depends first and foremost on Russia's behaviour."
“We are looking with great concern at the security situation on the Russian-Ukrainian border,” Mr Scholz said.
“Any violation of territorial integrity will have a high price and we will speak with one voice here with our European partners and our transatlantic allies,” he said.
There are fears that Russia is preparing to launch an attack on neighbour Ukraine, something Moscow denies.
Karen Donfried, the US State Department’s top official for Europe, was in Moscow on Wednesday. Moscow wants guarantees from Nato that the military alliance will not expand further eastward or deploy certain weapons systems in Ukraine and other countries that border Russia.
“American representatives were literally today handed concrete proposals in our foreign ministry that are aimed at developing legal security guarantees for Russia,” said Yuri Ushakov, a foreign policy adviser to the Kremlin and former Russian ambassador to the US.
“We are ready to start negotiations on this crucial issue immediately.”