Serbia has accused Germany of trying to amend the terms of Belgrade's European Union membership negotiations in a way that effectively would mean recognition of the independence of its former Kosovo province.
Berlin's envoy has dismissed the claims as "unfounded."
Serbian ministers have taken to the airwaves in Belgrade to denounce the alleged German moves as an attempt to "humiliate" their Balkan country.
Their claims are feeding an atmosphere of political crisis with conservative Prime Minister Aleksandar Vucic already looking toward an early election to cement his hold on power.
Kosovo declared independence from Serbia in 2008, almost a decade after NATO went to war to halt the killing and expulsion of ethnic Albanian civilians by Serbian forces fighting guerrilla rebels.
Serbia does not recognize Kosovo as sovereign, but signed up to an accord in 2013 designed to settle relations between the two as a condition of Belgrade's progress toward EU membership.
Implementation has been slow and politically unpopular in Serbia.
Based on reporting by Reuters and AP