The Republic of Ireland under-20s suffered a 2-1 friendly defeat to Slovakia in Devin today.
Brian Kerr's side took the lead after 27 minutes when Nottingham Forest youngster Liam Kearney found the net.
They held that lead until the 84th minute before Halenor snatched an equaliser for the home side.
Ireland then suffered another lapse in concentration just four minutes later when Pecovsky nipped in for the winner.
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Kerr's squad will take on the Czech Republic in Drnovice on Thursday.
The games have been arranged as preparation for the World Youth Finals which take place in the United Arab Emirates next Spring.