The EU is expected to put pressure on President Putin over Russia’s stance on Syria during a summit in St Petersburg.
Moscow has blunted Western efforts to condemn Syrian President Bashar al-Assad and push him from power during 15 months of bloodshed.
Both Russia and Europe say they still support Kofi Annan’s UN-backed peace plan, but EU nations would like Russia to press Assad harder to abide by a ceasefire demanded by the plan, and want him to step aside as part of a political transition.
EU foreign policy chief Catherine Aston said on Sunday that the crisis had reached a “critical point” and that Russia’s role was “crucial” to a solution.
Russia says it is not protecting Assad, who has given Moscow its firmest Middle East foothold, but that the Syrian leader’s exit cannot be a precondition for political dialogue.
Putin focused on the Russia-EU relationship as he opened Monday’s meetings, saying the wary neighbours should push to make progress toward a elusive new framework pact to govern their ties after four years of talks.
Putin ceded no ground on Syria in remarks during visits to Berlin and Paris on Friday, placing an accent on rebel violence, criticising sanctions and saying political decisions could not be forced upon the country from outside.
Chief Correspondent Alex Thomson goes in search of Houla's killers:
"I suppose a part of me feared hillside villages full of men with AK 47s and knives and a willingness to use both.
"In fact we found the usual and delightful warm hospitality of Syrians everywhere in the countryside. Valuable discussions over sweet Turkish coffee, the hookah pipe offered and several invitations to lunch.
Read more: In search of Houla's killers
Ashton, who met Russian Foreign Minister Sergei Lavrov on Sunday, said the EU wanted to “work closely with Russia to find a way to end the violence” and that “Russia’s role is crucial for the success of Annan’s plan”.
The statement said she spoke to Annan by phone on Sunday and that they agreed the crisis had reached a “critical point”.
Lavrov set a constructive tone in his own phone call with Annan, saying that to support the plan Moscow “will be ready to consider various scenarios of further work” that would help to coordinate international efforts on Syria, his ministry said.
However, when asked whether he expected the summit to narrow the gap on Syria, Lavrov told reporters: “I don’t think so.”