European diplomats told Russia on Friday that they were preparing further sanctions that would form part of a “harsh, robust” response if Russian troops invade Ukraine.
Tension over the Eastern European frontiers with Russia were raised further by an overnight cyber attack on the Ukrainian government and EU foreign ministers set out a 10-point approach to the crisis.
The framework shifts from dialogue with Russia to a warning of “massive consequences and severe costs” for Moscow if this fails.
The terms set out by Josep Borrell, the EU’s foreign policy chief, include a rejection of what he called a “Russian attempt to build spheres of influence in Europe”, after Moscow demanded a veto on expansion of Nato and amassed thousands of troops on its border with Ukraine.
British Prime Minister Boris Johnson and Turkey's President Recep Tayyip Erdogan discussed their “significant concerns" over the build-up of Russian troops on Friday.
Britain and Turkey are both Nato members with a strategic interest in the Ukraine-Russia issue but are not EU members.
“They shared significant concerns about the build-up of Russian troops on Ukraine's border and emphasised Nato's collective resolve to avoid further escalation,” a Downing Street representative said.
“They committed to continue working through Nato to reach a resolution. The leaders also agreed to further strengthen our bilateral security and defence co-operation.”
The US said it fears Russia has “pre-positioned” false flag operatives to carry out a provocation in eastern Ukraine.
Russia signalled impatience with the state of peace talks with the West on Friday after three separate summits this week ended with its demands refused.
EU ministers said they were ready for further dialogue, but Mr Borrell said Europe was simultaneously preparing to punish Russia if it attacks Ukraine.
“We will continue preparatory work on further sanctions in close coordination with like-minded partners,” he told a press conference after the EU summit in Brest, France.
Keen for the EU to pull its weight in discussions often dominated by the US and Russia, Mr Borrell said he was satisfied with American efforts to include Europe in its negotiations.
“We have been coordinating with the US and Nato. We have had an excellent cooperation before and after each meeting,” he told a press conference in Brest, France.
While Russia denies planning to invade Ukraine, diplomats issued increasingly dire warnings this week that the risk of war was at its highest in decades. The cyber attack affecting ministries in Kiev was interpreted by ministers as a potential prelude to military activity.
Ministers from Austria, Sweden and Denmark, as well as Mr Borrell, voiced suspicion that Russia could be responsible for the hack, in which menacing messages were left on Ukrainian government websites.
Russia, which is estimated by western powers to have about 100,000 troops massed on the Ukrainian border, has a long record of alleged cyber meddling in Ukraine and other countries.
“This is exactly the kind of thing that we have warned of and that we are afraid of,” said Swedish Foreign Minister Ann Linde.
“If there are attacks against Ukraine, we will be very harsh and very strong and robust in our response,” she said.
Ukraine said no personal data had been compromised, contradicting a threatening message left on the hacked governments websites in Ukrainian, Russian and Polish.
“All information about you has become public — be afraid and expect the worst. This is for your past, present and future,” it said.
The hack prompted Nato to say it would give Ukraine access to a malware database and was providing expert help from its Brussels headquarters.
Mr Borrell said he did not have proof of who was behind the attack but said: “We can imagine”.
Danish Foreign Minister Jeppe Kofod said he would “not be surprised” if the attack came from Russia.
Ministers said their preference was for diplomacy with Russia, with talks set to continue next week when German Foreign Minister Annalena Baerbock meets her Russian counterpart Sergey Lavrov in Moscow.
She said the trip was part of efforts to use every possible channel of communication, after talks between the US and Russia, Nato and Russia and members of the Organisation for Security and cooperation in Europe ended without a clear breakthrough.
“Especially in moments of crisis, diplomacy requires much stamina, patience and strong nerves,” Ms Baerbock told reporters.
She said: “We are doing everything to avoid any further escalation.”
Mr Lavrov, meanwhile, said on Friday that Moscow would not wait indefinitely for the West to hear its demands to limit Nato expansion.
“We have run out of patience,” Mr Lavrov said. “The West has been driven by hubris and has exacerbated tension in violation of its obligations and common sense.”