The United States has banned Britain from sharing intelligence from Washington with Ukraine as part of its withdrawal of support for Volodymyr Zelensky.

Donald Trump's decision to freeze American military aid to Kyiv yesterday brought warnings that Ukraine could run out of weapons in as little as two to three months' time.

But on top of missiles and ammunition, all UK intelligence agencies and military outlets also received an order expressly forbidding the sharing of US-generated intelligence, previously known as 'Rel UKR' - short for Releasable to Ukraine'.

Since the conflict began three years ago, the UK and other Western security partners such as Australia and New Zealand have shared such knowledge with Ukraine.

But the Mail has learnt the top-level security classification has now been removed by the United States pending further notification and is likely to impact upon Kyiv's ability to defend itself against Russia's continuing onslaught.

The ban affects the likes of the UK's GCHQ, the spy agencies and intelligence branches of the Ministry of Defence.

Last night, UK military intelligence expert Phil Ingram told the Mail: 'The United States's instruction to stop allies sharing US-derived intelligence with Ukraine is what I would expect.

'The US's intelligence partners, including Britain, have had their authority to pass on intelligence revoked.

'The US will tightly control distribution of its intelligence to Ukraine through agencies based in Kyiv.'

The move coincided with the US confirming it was pausing military aid to Kyiv as the rift between the two supposed allies deepened before Ukraine's president Volodmyr Zelensky offered US counterpart Donald Trump an olive branch yesterday.

Last night, a senior Ukrainian official told the Financial Times: 'We have two to three months. After that, the position will be very difficult for us.

'It will not be a total collapse, but we will be forced to withdraw from some areas more quickly'.

Critics suggested any long-term freeze would lengthen rather than shorten the war.

That is because it is expected to encourage the Kremlin to exploit Kyiv's dwindling weapons and ammunition stocks and launch a fresh bid for more territory.

Russia currently occupies around one fifth of Ukraine, including eastern provinces and the Crimean peninsula.

Ukraine is clinging on to a relatively small amount of territory it seized last year in the southern Russia province of Kursk.

Currently, Ukrainian and Russia troops are facing off along a 600-mile frontline, which has gradually been pushed deeper into Ukraine due to Russian advances.

The decision to suspend military aid came three days after a dramatic clash in the Oval Office between presidents Trump and Zelensky.

To date, the US has provided military aid worth £53 billion to Ukraine, compared to Europe's combined total, which includes Britain, of £51 billion.

While, in theory, Europe could eventually double its support for Ukraine - and use frozen Russian assets to pay for weapons - the US supplies a lot of high-end equipment that other states do not possess.

The impact of the suspension of military aid could be felt first by Ukrainian civilians should US-gifted Patriot defence missile systems run dry and leave Kyiv unable to protect its skies from Russian bombardments.

Last night, Nato allies expressed regret over the decision. Finnish Foreign Minister Elina Valtonen told a thinktank in London 'we need the Americans militarily.

'This definitely shouldn't be a moment where we give in. As on the battlefield, Russia has not really been advancing in recent months.'

French prime minister François Bayrou said the freeze on aid was akin to abandoning Ukraine in favour of a Russian victory.

He told French senators: 'The word 'suspension' fools no one.

'The suspension in war of assistance to an aggressed country signifies that the aggressed country is being abandoned and that one accepts — or hopes — that its aggressor wins. It is obviously unbearable.'

Unsurprisingly, the White House's move was welcomed in the Kremlin, where Vladimir Putin's spokesman Dmitry Peskov said: 'If the US stops or suspends supplies, this will probably be the best contribution to the cause of peace.'

According to Western officials, about 20 per cent of military hardware in the Ukraine comes from the US. Some 25 per cent comes from Europe, including the UK and other nations. About 55 per cent is funded by Ukraine and comes from Ukrainian production.

The pause includes all US military equipment not currently in Ukraine, including weapons in transit and at bases in Poland. It will affect more than £790 million in arms and ammunition, such as rockets, anti-tank weapons and armoured vehicles.

Even before the pause, Ukraine was outnumbered three to one on troops, five to one on artillery and ten to one on artillery vehicles compared to Russia.

Artillery, GPS-guided missile systems and Patriot air defence systems, provided by the US, are deemed essential if Ukraine wants to stave off certain defeat.

Even some sophisticated UK weapons systems, including Storm Shadow cruise missiles rely on the US to hit the right targets.

Matthew Savill, director of military sciences at the Royal United Services Institute (RUSI) said Storm Shadow need the dummy missiles provided by the US to interfere with Russian air defences.

The highly advanced £750 million Patriots are crucial for protecting Ukraine's skies and can do Russia's most advanced ballistic missiles including its air-launched hypersonic Kinzhal.

For this reason, the UK's Prime Minister Sir Keir Starmer is determined to secure Patriot as part of a US air-cover package for any UK-led European peacekeeping force.

To date, the US has provided Ukraine with more than 40 High Mobility Artillery Rocket Systems (HIMARS), more than 200 Howitzers and more than 300,000 155mm artillery rounds.

It has also sent more than 3 million 155mm artillery rounds, more than 7,000 precision-guided 155mm artillery rounds, 1 million 105mm artillery rounds and more than 400,000 152mm artillery rounds.

The US has also gifted more than 700,000 mortar rounds, 31 world-leading Abrams tanks, more than 300 Bradley fighting vehicles and around 2,000 armoured personnel carriers.