The US is to activate a land-based missile defence station in Romania, which will form part of a larger and controversial European shield.

Senior US and Nato officials are expected at the ceremony in Deveselu, southern Romania.

The US says the Aegis system is a shield to protect Nato from short and medium-range missiles, particularly from the Middle East.

But Russia sees it as a security threat - a claim denied by Nato.

Relations between the West and Russia have deteriorated since Moscow's annexation of Ukraine's southern Crimea peninsula in 2014.

Russia is also accused of arming separatists in eastern Ukraine and sending its troops there - a claim denied by the Kremlin.