World leader Omar McLeod of Jamaica looks the pick of the field going into the final later on Tuesday after leading the qualifiers from the three semi-final races.
Spain’s Orlando Ortega claimed victory in a scrappy opening semi-final by 0.04 in a time of 13.32, with USA’s Ronnie Ash securing the second automatic qualification spot.
In a messy race, which saw Haiti’s Jeffrey Julmis takes a heavy tumble at the first hurdle, little separated the field at halfway.
Andrew Pozzi of Great Britain dropped out of contention after clattering through a hurdle mid-race but, as the race progressed, Ash and Ortega took control with the Spanish athlete being rewarded for a more aggressive finish to grab the victory and a more central lane draw for the final.
Behind the leading pair, Poland’s Damian Czykier grabbed third in 13.50 with European silver medallist Balazs Baji of Hungary fourth in 13.52, although neither made the cut for the final.
In a much higher quality second semi-final, McLeod cemented his standing as the gold medal favourite with an assured win in a handy 13.15.
The Jamaican was even with France’s Pascal Martinot-Lagarde and US champion Devon Allen over the first few hurdles, but gradually the 22-year-old, who is seeking his country’s first Olympic gold medal in this event, gradually pulled clear and by the finish line had opened up a 0.10 advantage from Martinot-Lagarde, the second automatic qualifier.
Allen, a stellar talent but lacking in big-time experience, had to settle for third in 13.36 but advanced on time along with Johnathan Cabral of Canada, fourth in 13.41.
Dimitri Bascou ensured a second French athlete advanced to the final with an accomplished semi-final win in 13.23.
The European champion was the class of the field. Behind him, Milan Trajkovic created history to became the first Cypriot to reach an Olympic track final by taking 0.08 from his national record to clock 13.31 for second.
The best of the rest was USA's Jeff Porter, but his time of 13.45 was not quick enough to advance him to the final as a non-automatic qualifier.
The final takes place later on Tuesday at 22:45 local time.
Steve Landells for the IAAF