Three South Korean pharmaceutical firms will soon be allowed to produce generic versions of the anti-impotence drug Viagra despite a row over patents, officials said Wednesday. The Korea Food and Drug Administration said generic products made by the three local firms have passed a \"bioequivalence\" test. \"The three firms are expected to get approval for production of Viagra generics probably this month or later,\" an official in charge of medicine tests told AFP on condition of anonymity. \"Our move has nothing to do with an ongoing patent row,\" he said, adding the watchdog is also expected to give the go ahead for more local firms. Numerous domestic pharmaceutical firms have applied for approval to manufacture Viagra generics since it was introduced in South Korea in 1999. US pharmaceutical giant Pfizer claims its patent, which involves using sildenafil, is valid until May 2014. \"Our patent covering the material is still valid,\" a Pfizer official in Seoul said, urging South Korean firms to recognise it. Pfizer has yet to counter a lawsuit filed by CJ Cheiljedang, a domestic pharmaceutical firm seeking to invalidate the patent. \"We plan to produce a generic Viagra regardless of the court\'s ruling, even if we have to compensate Pfizer in the future,\" an unnamed CJ Cheiljedang official told Yonhap news agency.