A top diplomat trying to settle the future status of Kosovo says the Serbs and ethnic Albanians may be facing their last chance to reach a deal.
The German ambassador in London, Wolfgang Ischinger, said they would be to blame if the talks ended in failure.
EU, Russian and US experts are meeting in London to discuss Kosovo.
"We... are offering Belgrade and Pristina another opportunity - maybe the last opportunity - to work out a negotiated solution," he told the BBC.
"If there is success of this effort, it will be their success, if there is failure of this process, it will be their failure," he said on the BBC Radio 4 Today programme.
On Friday, Mr Ischinger will travel to the Balkans with his US and Russian counterparts for talks with Serbian leaders and the interim administration in Kosovo, where the ethnic Albanian majority wants independence.
Diplomacy has shifted to the Contact Group - made up of envoys from Russia, the US, UK, France, Germany and Italy - since Russia opposed a UN plan to give Kosovo "supervised independence".
Serbia - traditionally an ally of Russia - rejects the independence plan.
Kosovo, legally still part of Serbia, has been governed by the UN since 1999. Serb forces pulled out after Nato air raids, launched to halt a Serb crackdown on ethnic Albanians, some of whom had taken up arms.