Media playback is unsupported on your device Media caption Philip Hammond: There must be ''no let-up'' in the pressure on Russia

The UK is not planning to send arms to Ukraine but it cannot allow its armed forces to collapse, the foreign secretary has said.

Philip Hammond told the Commons there needed to be "a diplomatic solution" to the conflict but the UK would keep its no-arms decision "under review".

His statement comes amid an escalation in fighting between government forces and pro-Russian separatist rebels.

The US has said it has not ruled out sending "lethal defensive weapons".

Ukraine's Western allies accuse Russia of sending in troops and armour to help the rebels - an allegation repeatedly denied by the government in Moscow.

The leaders of Ukraine, Russia, France and Germany are due to meet on Wednesday to hammer out a peace deal.

'Profound suffering'

In a statement to the Commons, Mr Hammond said fighting in the eastern regions of Ukraine resembled a "small-scale conventional war".

He said Britain supplied non-lethal equipment - such as helmets, body armour and fuel - to the Ukrainian armed forces to help prevent causalities, and it was up to each country in the Nato alliance to decide whether to supply lethal aid.

"The UK is not planning to do so but we reserve the right to keep this position under review. Different members of the alliance take nuanced positions on this question and are entitled to do so," he said.

"However, we share a clear understanding that, while there is no military solution to this conflict, we could not allow the Ukrainian armed forces to collapse."

US President Barack Obama said on Monday he had not ruled out supplying "lethal defensive weapons" to Ukraine if diplomacy failed.

Labour MP and former Foreign Secretary Jack Straw said Russia "would regard any provision of lethal aid" by an individual country as a Nato decision and would "respond in a similar way".

Shadow foreign secretary Douglas Alexander called the Ukraine crisis "a conflict of profound civilian suffering".

"We must continue with a robust and united international response," he told the Commons.

Fighting started in eastern Ukraine in April 2014 and raged for months until a deal was struck between the government and the separatists.

But the ceasefire never held entirely and the start of this year saw the rebels begin a new push to take control of more areas.

Mr Hammond told the Commons more than 5,000 people are estimated to have been killed since the crisis began and more than 1.5m people displaced.

"In recent weeks, Russia has aggravated the effects of its initial incursion by stepping up the military support it provides to its proxies," he said.

Last week, Defence Secretary Michael Fallon announced that the UK would play a lead role in a "high- readiness" Nato force that would be established in Eastern Europe.

Britain will send up to 1,000 troops and four RAF Typhoon jets for "air policing" across the Baltic states.