ISTANBUL — Buoyed by support from his country’s NATO allies, Prime Minister Recep Tayyip Erdogan warned Syrian forces on Tuesday to stay clear of their troubled border or face a Turkish military response to any perceived threat, following the disputed downing of a Turkish warplane.

The Turkish leader’s bellicose tone came as ambassadors from the NATO alliance, seeking to avoid a wider conflict, held emergency talks in Brussels at Turkey’s behest. After the meeting, the NATO secretary general, Anders Fogh Rasmussen, said the alliance considered Syria’s actions inshooting down a Turkish warplane last Friday “unacceptable.”