The UK should consider arming Ukraine as the war with pro-Russian separatists continues to rage in the east of the country, according to a former head of the army.
Speaking on Sky's Murnaghan programme, Air Chief Marshal Lord Stirrup accused Russian President Vladimir Putin of running a "gangster regime" and "gangster foreign policy".
When asked whether the UK should provide weapons for Ukrainian soldiers, Lord Stirrup said: "That is something we need to think about it carefully. There are arguments on both sides.
"If we work to do that it needs to be part of a long-term strategy, not just a short-term knee jerk response.
"It might be appropriate. It is something we need to think about."
Lord Stirrup also warned in his interview that NATO is viewed as "weak" by Mr Putin, adding the West needs a long-term strategy to combat Russia's actions with regards to its neighbour.
He said: "Putin views the West as weak all round and that is a very, very dangerous position for us to be in.
"My concern is that NATO is not spending enough resource on defence."
In recent weeks, RAF jets have twice intercepted Russian planes which were spotted off the coasts of Cornwall and Bournemouth.
Lord Stirrup said Moscow is becoming more aggressive, and testing British defences with "mission rehearsals".
This "very dangerous" game raises the possibility of a mid-air collision Russian aircraft and civilian aircraft, he added.
His comments come after the former defence secretary Liam Fox said the UK should provide sophisticated arms, including drones, to Ukraine.
However, this was ruled out by the Leader of the Commons, William Hague, who said the best approach was to increase sanctions if Russia continues to destabilise Ukraine.
"We are not planning as the UK to send arms to Ukraine, Mr Hague told the BBC's Andrew Marr Show.
"It hasn't been our approach in any recent conflict in recent years to send arms into those conflicts."
Moscow has long been accused by the West of supporting the rebels since the conflict broke out last April, a claim Russia denies.
A ceasefire between the government and the separatists has broken down amid fierce fighting for the strategically important town of Debaltseve.
On Sunday, Ukrainian forces began the process of withdrawing heavy weapons from the frontline in agreement with separatists .