Britain and the US are considering implementing economic sanctions against Russia and Syria over bombings in Aleppo.
Foreign Secretary Boris Johnson warned that Russian president Vladimir Putin and his regime can be made to ‘feel the consequences of what they are doing’.
Speaking alongside his American counterpart, secretary of state John Kerry, the pair condemned Russia’s military support of Bashar Assad’s government.
Acknowledging that military intervention, such as a no-fly zone over Aleppo, would be ‘extremely difficult’, Mr Johnson said the West can work with the diplomatic ‘tools we have’.
Mr Kerry said: ‘It could stop tomorrow morning, tonight if Russia and the Assad regime were to behave according to any norm or any standard of decency, but they’ve chosen not to.
‘Instead we see what can only be described as crimes against humanity taking place on a daily basis, and hospitals are bombed and children are bombed or gassed.’
The pair made fresh calls for a ceasefire following talks in London.
Mr Johnson said Russia and Syria’s ‘barbaric siege’ of Aleppo, where 275,000 citizens face bombings every day, would not be successful, as he discussed what options remain open to the West.
He said: ‘No option is in principle off the table but be in no doubt that these so-called military options are extremely difficult and there is, to put it mildly, a lack of political appetite in most European capitals and certainly in the West for that kind of solution at present.
‘So we’ve got to work with the tools we have – the tools we have are diplomatic.
‘I think the most powerful weapon we have at the moment is our ability to make president Putin and the Russians feel the consequences of what they are doing.’