Guerrero, who tested positive for cocaine metabolite benzoylecgonine last October, had his six-month ban extended to 14 months last week following an appeal by the World Anti-Doping Agency, reports Xinhua news agency.
In a social media post, FIFPro said it hoped "for a breakthrough in the next 24-48 hours."
Last Monday's decision by the Court of Arbitration for Sport (CAS) rules the 34-year-old Flamengo striker out of the World Cup in Russia, which starts on June 14.
Peru qualified for the tournament for the first time in 36 years by beating New Zealand in an inter-continental playoff last November.
Guerrero, who says he unwittingly consumed the substance in contaminated tea, has said his lawyers are "considering all options" to contest the CAS decision and clear his name.
FIFPro last week described the ruling as disproportionate and inconsistent with the facts presented during the case.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
