Peter Pellegrini, a close ally of left-wing populist Prime Minister Robert Fico, was sworn in as president of Slovakia on Saturday. The 48-year-old took the oath of office in a ceremony at the Slovak Philharmonic in Bratislava in front of members of parliament. Pellegrini won the run-off election in April with 53.1% of the vote, beating out former foreign minister Ivan Korčok. Ukraine featured prominently in the campaign, with Pellegrini advocating a cautious stance on arms deliveries to Kiev – a position that is in line with Russia-friendly Fico. Pellegrini previously served as prime minister…