Belarus marked their first appearance at a major tournament since gaining independence 21 years ago with victory over New Zealand in an Olympic Games Group C clash at the City of Coventry Stadium.
An error of judgment by stand-in Kiwis keeper Michael O'Keeffe gifted Belarus midfielder Dmitry Baga the only goal on the stroke of half-time.
New Zealand, who had Ipswich defender Tommy Smith booked inside the first 30 seconds, were the first to threaten when West Brom striker Chris Wood's downward header was saved by Aleksandr Gutor. Gutor also tipped over Marco Rojas's 30 yard drive but Belarus looked increasingly dangerous in front of the 14,000 crowd.
Former Blackpool loanee Sergei Kornilenko was denied by Michael McClinchey's close range block and O'Keefe turned aside Baga's dipping effort.
Then seconds before half-time O'Keeffe, who replaced injured first choice keeper Jake Gleeson, failed to punch clear a Renan Bardini Bressan corner and Baga headed home at the far post.
Wood should have equalised after 67 minutes only to shoot over with just Gutor to beat, but O'Keeffe was still the busier of the two keepers.
He partially atoned for his error by parrying Kornilenko's shot on the turn and producing reflex saves to keep out two attempts from substitute Andrei Voronkov, but O'Keeffe was relieved when Kornilenko's late drive struck the bar.