The Mongolian made the better start, going to work on the body of the British captain. Stalker struggled to settle into the contest but managed to keep the scores level at 6-6.
Stalker improved in the second round, but still found Uranchimeg more than a handful. The Mongolian's work rate helped him establish a one-point lead as they entered the decider.
The Liverpool fighter launched a desperate assault from the third bell as he strived to keep his Olympic medal hopes alive. He landed a number of heavy blows as Uranchimeg began to run out of legs.
A barnstorming final round came to a close with both men believing that they had done enough to win.
However, the judges sided with Uranchimeg and awarded him a narrow 23-22 verdict.