Syria is expected to dominate the agenda when Russian and EU leaders hold talks in St. Petersburg on June 4.
EU officials are expected to press President Vladimir Putin to shift stance on Russia’s ally during the summit on the outskirts of the city.
European Council President Herman Van Rompuy, European Commission President Jose Manuel Barroso, and EU foreign policy chief Catherine Ashton are among those attending.
On June 3, Putin hosted the EU leaders for an informal dinner.
EU members want Moscow to put pressure on Damascus to comply with UN-Arab League envoy Kofi Annan's peace plan and withdraw heavy weapons from cities.
Ashton, who held talks with Russian Foreign Minister Sergei Lavrov on June 3, said in a statement: "Russia's role is crucial for the success of Annan's plan."
Russia, along with China, is resisting Western calls to condemn President Bashar al-Assad, insisting his removal cannot be a precondition for political dialogue.
During a visit to Stockholm on June 3, U.S. Secretary of State Hillary Clinton said she had told Lavrov in a phone call that Assad's departure “does not have to be a precondition.”
"I made it very clear that there would be no point to any meeting unless it included all elements of Kofi Annan's plan," Clinton said. "And that certainly means we have to focus on a path forward for a political transition. Assad's departure does not have to be a precondition, but it should be an outcome, so that the people of Syria have a chance to express themselves.”
Also on June 3, Assad told parliament that "foreign meddling" was to blame for Syria's divisions and reiterated that the only way to resolve the crisis was through political dialogue.
The Russian and EU leaders were also expected to discuss trade and Iran's controversial nuclear program during the St. Petersburg summit.
Moscow will also be looking to speed up progress toward visa-free travel.
European diplomats regard the Russia-EU summit as a chance to renew ties with Putin following his return to the Russian presidency on May 7.
With reporting by AFP, dpa, and Reuters