The Azkals advanced after winning 3-2 on aggregate, but not before surviving intense pressure from the Mongolians in a match played at temperatures ranging -5 to -7 degrees Celsius.
The Filipinos came into the game holding a 2-nil cushion, but as promised, they refused to sit on that lead as James Younghusband opened the scoring with a close-range strike in the 4th minute.
But the Azkals lost their grip of the game and from a set piece, the Mongolians equalized through skipper Lumbengarav Donorov in the 22nd minute.
Growing in confidence, the Mongolians finally went ahead 10 minutes later as Garidmagnai Bayasgalan followed up his saved penalty to beat Azkals stand-in keeper Eduard Sacapano.
Despite the loss, the Azkals advanced to the group qualifying starting March 21 in Rangoon, Myanmar. There, the Azkals will play Myanmar, Bangladesh and Palestine with the top two teams making the eight-team final tournament next year.