"We expect President Putin, who has backed President Assad with huge amounts of military and political commitment, we expect him to be able to get control of Assad, and at the moment it does not look like he is in control of Assad," Hammond said ahead of an EU Council meeting in Brussels, as quoted by the UK Foreign Office.
He added that the European Union should "manage" its relations with Russia, and not forget that Moscow is "a challenge…. to our values and to our security."
Syria has been in a state of civil war since 2011, when mass anti-government protests against Assad and his ruling party escalated to an armed confrontation between government troops and allied militia on the one hand, and Syrian opposition factions on the other.
Unlike the West, Russia has been supporting Assad as the legitimate Syrian authority, and is contributing to finding a political solution to the crisis in the conflict-hit country, including by mediating intra-Syrian talks and helping to organize international meetings and consultations on the issue.
Since late September 2015, Russia has been conducting airstrikes on IS positions in Syria, following a request from Assad.