Fernando Santos acknowledged European champions Portugal and 2010 World Cup winners Spain assume favouritism in Group B, though he refused to underestimate Morocco and Iran.
Portugal and neighbouring Spain will go head-to-head at the World Cup in Russia next year, along with Morocco and Iran following Friday's draw.
Cristiano Ronaldo's Portugal – who claimed Euro 2016 – and Spain headline the group but Santos is wary of Morocco and Iran, who made it through their respective CAF and AFC qualifying campaigns undefeated.
"It's a very deceptive and treacherous group. Portugal have to accept that we are one of the favourites but if you look in a bit more detail, you can see it's very difficult," Santos said.
"Spain are naturally favourites, as I've always said."
Santos added: "Morocco have scored goals and conceded none. This shows the strength of the team, there are players who have already played in Portugal, [Mehdi] Benatia who played for Juventus, and the quality of the coach.
"Iran had a good qualifying campaign, the second time they are in the World Cup, have experience and the coach also, maybe one of the most experienced of this World Cup. Also had a good performance, no defeat, conceded goals only in the last game when it was already qualified. It's going to be a difficult tournament."
Portugal and Spain will face-off at Fisht Olympic Stadium in Sochi on June 15, while Morocco and Iran clash in Saint Petersburg.
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