Chris Coleman says Wales must win their remaining four qualifiers to top their World Cup group.
Wales held Group D leaders Serbia 1-1 in Belgrade on Sunday night after Aaron Ramsey's penalty had given them a half-time lead.
Aleksandar Mitrovic equalised 17 minutes from time to keep Serbia four points ahead of third-placed Wales with four games to play.
The Republic of Ireland stay second level on points with Serbia after being held 1-1 at home by Austria.
"I think realistically if we want to finish first, (we need) four wins," manager Coleman said.
Wales will resume their programme at home to Austria and away to bottom-placed Moldova in September. Joe Allen will be missing for the Austria game in Cardiff after picking up a second booking in the competition. But at least Coleman should be able to call on Real Madrid forward Gareth Bale, who missed the frenetic Belgrade draw through suspension.