By Renee Maltezou ATHENS (Reuters) - Greek centrist Stavros Theodorakis says his small Potami party is willing to strike a pact with leftists, conservatives or even "the devil" if needed to save the country from yet another round of elections after it votes later this month. Opinion polls show the leftist Syriza party and conservative New Democracy neck-and-neck before the elections on Sept. 20 - suggesting no outright winner will emerge and sending Greeks back to the ballot box for a third time this year, unless a coalition is cobbled together. Alexis Tsipras forced the election last month by resigning as prime minister after only seven months in office, hoping to end a rebellion in his Syriza ranks and win an outright majority.