Iran called the deployment of Saudi and Emirati troops in Bahrain unacceptable, warning Riyadh and its ally Washington of "dangerous consequences" for intervening in this crisis.
But the troops have been sent at a request from the Bahraini government which condemned Iran's comment and withdrew its ambassador to Tehran.
The troops have been dispatched as a part of the Gulf shield forces, jointly formed by the Gulf Cooperation Council (GCC). The GCC includes a mutual defense agreement against possible internal and external subversion.
But are the neighbouring countries deploying troops to Bahrain containing regional instability or spreading it?
Joining us to discuss these issues are: Simon Henderson, the director of the Gulf and energy policy programme at the Washington Institute for Near East Policy; Hussein Shobokshi, a columnist at Asharq Alawsat newspaper; and Ghanbar Naderi, a journalist and political analyst.
This episode of Inside Story aired from Wednesday, March 16, 2011.