Russia must halt "unacceptable" meddling in other countries, especially the Balkans and Ukraine, for there to be any chance of a fresh start with the West, British foreign minister Boris Johnson said Monday.
"Let us be very clear, Russia is up to all sorts of no good," Johnson said as he arrived for an EU foreign and defence ministers meeting in Brussels.
"They are engaged in cyber warfare, engaged in undermining countries in the Western Balkans -- you have seen what happened in Montenegro -- to say nothing of what has happened in eastern Ukraine," he said.
"It is completely unacceptable ... they have got to change, they have got to show that they can be trusted again," he said.
But Johnson, due to visit Moscow shortly, also said no one in Europe or the United States wanted to see a return to Cold War days.
The aim instead must be to "try to engage with the Russians, to try to understand where they are coming from... to get them back on to a better path."
The 2014 Ukraine crisis plunged ties with Moscow into a freeze reminiscent of the worst days of the Cold War and relations have been badly strained ever since.
Repeated efforts to enforce a ceasefire in eastern Ukraine between government forces and pro-Russian rebels have failed. Western leaders believe Moscow manipulates the fighting to put pressure on them and Kiev.
EU efforts to forge closer ties with the Balkan states meanwhile have stalled, with Brussels seen as failing to deliver on promises of membership and economic progress.
Like Johnson, other EU member states also see Russia's hand in recent developments, especially in Serbia where Moscow backs its traditional ally in Belgrade in not recognising Kosovo's independence.
EU foreign affairs chief Federica Mogherini was heckled in the Serbian parliament during a visit last week during which she highlighted the EU's efforts to normalise ties between Serbia and its breakaway province.
The EU's 28 national leaders will discuss the Western Balkans at a summit in Brussels on Thursday.