Portugal must beat Bosnia-Herzegovina to reach the 2012 European Championship after UEFA conducted the playoffs draw on Thursday.
Cristiano Ronaldo and his teammates will travel to Bosnia for the first leg next month in what is a rematch of the countries' 2010 World Cup playoff, which Portugal won 2-0.
Ireland was drawn to play away first against Estonia, which has never reached the finals of a major tournament.
Euros debutant Montenegro will host the second leg against the Czech Republic, while Turkey, a Euro 2008 semifinalist, faces Croatia first in Istanbul.
First-leg matches will be played Nov. 11 or 12. Return games are scheduled Nov. 15.
Winners will complete the 16-nation lineup at the June 8-July 1 tournament co-hosted by Poland and Ukraine in eight cities.
Bosnia advanced to the Euro 2012 playoffs despite almost being kicked out of the tournament while suspended by FIFA and UEFA for two months last season over political issues.
Ireland returns to a major playoff two years after a controversial World Cup defeat by France, and drew the lowest-ranked unseeded opponent.
Estonia is 37th in UEFA's 53-nation European standings and advanced to the playoffs despite losing 2-0 against the Faroe Islands in qualifying.
Montenegro is playing in its first European Championship after being recognized as world football's newest nation in 2007.
Turkey was unseeded in the draw despite a memorable run at Euro 2008, and is coached by Dutch great Guus Hiddink who led Russia to the 2008 semifinals.
The finals tournament draw is made Dec. 2 in Kiev.
Poland and Ukraine are given automatic top-seeding in their four-team groups, and defending champion Spain and the Netherlands also have No. 1 status.
Germany, Italy, England and Russia will be the No. 2 seeds.
Greece, the 2004 champion, Sweden, and Denmark are likely No. 3 seeds.
France, the 2000 winner, will be fourth-seeded unless the playoffs produce a series of upset victories.