US concerned by Russia?s Syria moves US Secretary of State John Kerry has expressed concern to Moscow over reports of Russian military build-up in Syria, the state department says.US media reports said Russia has sent advisers and hardware to Syria, in what Washington fears is an expansion of its support for President Bashar al-Assad.Any such development would "escalate the conflict", Mr Kerry told his Russian counterpart Sergei Lavrov.Russia has been a key ally of Syria throughout its four-year civil war.