The European Union and Russia launched a full day of talks on Tuesday dominated by a far-ranging dispute over the Syria crisis and Brussels' decision to lift its arms embargo on President Bashar al-Assad's foes.
EU dignitaries said Russia's human rights record would also come under the microscope at meetings in the industrial Ural Mountains city of Yekaterinburg.
Russian President Vladimir Putin attempted to build on his rapport with the visiting duo of European Council President Herman Van Rompuy and European Commission head Jose Manuel Barroso when he hosted a dinner late Monday ahead of the full day of talks.
He opened Tuesday's session without mentioning Syria and instead underlined the booming trade between the two sides.
Moscow is also hoping to eventually secure visa-free travel to Europe and win a release for its natural gas giant Gazprom from new rules that forbid it from owning pipelines and other facilities in EU states.
"It is obvious that our energy dialogue may only advance successfully if we take our mutual interests into account," Putin told his EU partners at the start of Tuesday's session.
"Another problem requiring our full attention is the preparation of a new framework Russia-EU agreement," he added in reference to talks that have dragged on for years.
"Right now, both sides are interested in finishing this job as soon as possible."
The framework agreement -- the basis of Russian-EU cooperation in all areas of trade -- has not been updated since the two sides first established relations after the Soviet Union's collapse.
Yet no other issue has been as divisive as the European Union's strong backing of the Syrian opposition and Putin's continued support for a regime with which Moscow has been allied since the Soviet era.
"The subject of Syria will be one of the priority areas at the talks," Moscow's EU envoy Vladimir Chizhov said.
Russia's Defence Minister Sergei Shoigu even went so far as to suggest that the EU's decision to lift its embargo on arming Syria's rebels untied Moscow's hands to supply weapons to Assad which had been banned by international treaties.
Analysts believe Moscow and Brussels may try to smooth out the row by issuing a statement of support for a proposed peace conference on the crisis that is meant to get Assad's camp and the opposition involved in direct talks for the first time.
"The EU is convinced that there is no alternative to a political solution to the crisis," Van Rompuy said at the start of Tuesday's session.
The European Union intends "to strengthen its cooperation with Russia on the Syria issue," he stressed.
It is less clear how the two sides intend to resolve their growing differences over the powerful role enjoyed by Russian natural gas giant Gazprom in the European market.
Russia accounts for about a third of the 27-nation bloc's gas supplies -- a dominance that has allowed Gazprom to dictate prices for many years.
The dispute culminated in an EU decision in September to launch a probe into Gazprom's pricing strategy.
Putin's foreign policy adviser Yury Ushakov called the action against Gazprom "discriminatory".
Analysts said the Gazprom issue is particularly dear to Russian leaders who rely on energy exports to help promote their foreign policies and fill coffers for social spending at home.
"We can forget about seeing the signature of a framework Russia-EU agreement until they settle the issue of working around Europe's new natural gas rules," said Olga Potyomkina of the Russian Academy of Sciences' Institute of Europe.
But the tensions could soar even higher when EU leaders raise the issue of Russia's rights record under Putin's 13-year rule.
EU foreign policy chief Catherine Ashton said Brussels was particularly concerned about a new crackdown on non-governmental organisations with foreign funding. They are now forced to wear a "foreign agent" tag.