Peru captain Paolo Guerrero will miss the World Cup after the Court of Arbitration for Sport upheld an appeal by the World Anti-Doping Agency to increase the length of his drugs ban.

Guerrero was initially banned for 12 months after testing positive for benzoylecgonine, a metabolite of cocaine, following Peru's World Cup qualifier with Argentina in October last year.

Accepting Guerrero's argument that the substance was accidentally consumed in contaminated tea, FIFA reduced the ban to six months, a period which would have enabled Guerrero to play in Russia, and he was duly named in Peru's provisional squad on Sunday.

But CAS have increased Guerrero's suspension from six to 14 months on the basis that he did bear "some fault or negligence" for the positive test, and must therefore face a ban of between one and two years under FIFA's own anti-doping rules.

A CAS statement read: "The CAS panel confirmed the existence of an ADRV [anti-doping rule violation] committed by Mr Guerrero, but also accepted that he did not attempt to enhance his performance by ingesting the prohibited substance.

"However, the panel considered that the player did bear some fault or negligence, even if it was not significant, and that he could have taken some measures to prevent him from committing the ADRV.

Paolo Guerrero will not be able to play at the World Cup. EPA/German Falcon

"Considering that, in case of no significant fault or negligence, the sanction should, in accordance with the applicable FIFA rules, be in the range of one to two years of suspension, the CAS panel considered that the appropriate sanction would be 14 months in light of the Mr Guerrero's degree of fault."

Guerrero had also filed a case to CAS in an effort to be absolved of the original sanction, which ended this month. His case and that of WADA were consolidated into a single case in Lausanne.

Guerrero's absence will be a big blow for Peru, who are preparing for their first World Cup finals since 1982.

Capped 86 times for his country, the experienced striker plays for the Brazilian club Flamengo.