The hosts Wales were unremarkable throughout in their fourth Group D encounter, but Bale’s first-half strike appeared to have clinched three crucial points.
However, with just five minutes remaining, Mitrovic headed Serbia level to leave Wales four points off the pace set by the Republic of Ireland, who Coleman’s men face next in March.
Bale, though, still believes his side can progress to the finals from this difficult position, having reached the last four at Euro 2016.
“We are so disappointed at the moment, we played great in the first half but then we faded,” he told Sky Sports. “We dug in. It’s one of those things, you go so close at one end [as Bale hit the post] and then they go up and score.
“We believe we can still do it, we just need to keep working hard. At home we were confident, we were 1-0 up in the 85th minute, it’s two points lost.”
Wales travel to Ireland in their next qualifier on March 24.