By Agustin Geist, Nicolás Misculin and Adam Jourdan BUENOS AIRES (Reuters) -Argentina has struck an agreement in principle with the International Monetary Fund over a new $44.5 billion standby deal, both sides said on Friday, a major breakthrough in tense talks to restructure loans the country cannot repay. The South American country has been locked in talks for over a year with the IMF over a new program to revamp debt outstanding from a failed $57 billion loan deal from 2018, the fund’s largest ever. It faced a $700 million payment due Friday. “We had an unpayable debt, which left us without…