Mounting tensions between Ukraine and Russia has led the Foreign Office to begin withdrawing some staff and dependents from the embassy in Kyiv.
Here we look at the background to the situation and what might happen next:
What is the cause of the tension between Russia and Ukraine?
Ukraine declared independence from the Soviet Union in 1991 but maintained close economic and cultural links with Russia.
Alarmed by Ukraine’s move towards closer ties with the European Union and a popular uprising which forced out Moscow-leaning president Viktor Yanukovych, Russia annexed the strategically important Crimean peninsula in 2014.
Mr Putin wants Ukraine to remain inside Russia’s sphere of influence, its “near abroad”, and to avoid becoming a Western-style democracy with ties to the European Union and Nato.
What has caused the latest crisis?
Russia has denied any intention to invade Ukraine, but has massed an estimated 100,000 troops along the country’s border.
Troops are also taking part in exercises in Belarus, which borders Ukraine to the north.
The UK has also accused Russia of increased cyber activity and widespread disinformation, as well of plotting to install a puppet government in Kyiv, something dismissed as “nonsense” by Moscow.
What has been the response?
Western nations have responded by threatening sanctions against Russia and supplying arms to the Ukrainian forces.
The UK has around 100 troops providing training, although this number fluctuates, as part of Operation Orbital.
Defence Secretary Ben Wallace confirmed the UK would supply “light, anti-armour, defensive weapon systems” to the Ukrainian forces, while the US has also sent what it described as “lethal aid” including ammunition.
The Nato alliance is increasing the number of warships and fighter jets in eastern Europe.
Could war be prevented?
US secretary of state Antony Blinken and Russian foreign minister Sergey Lavrov met in Geneva on January 21 and although there was no breakthrough the diplomatic path does not yet appear to have been closed off.
But one of Mr Putin’s key demands is for a guarantee that Ukraine will never be admitted to Nato, something that the allies will not promise, saying that such matters are decisions for Kyiv and the Nato members.
US President Joe Biden has warned that any invasion would result in Russia paying a “heavy price”, with severe economic sanctions although he also hinted at divisions in the West about what the response might be to a “minor incursion”.
What is the Foreign Office doing in Kyiv?
An update to travel advice revealed that some British staff and dependents are being withdrawn from the embassy in Ukraine’s capital because of the “growing threat from Russia”.
The US State Department was taking similar action, ordering the departure of family members from its embassy due to the continued threat of military action.