Britain's deputy Prime Minister has declared the war in Ukraine is "in the balance" while warning the conflict will last for months or even years to come.

Appearing on Sky News, Dominic Raab said officials are doing everything in their power to "deter Putin's behaviour" as the war entered its third month.

Predictions are now stretching to the Ukraine war lasting years as Russia refuses to work with the West and continues its attacks.

Raab said some European countries "need to step up to the plate" and insiders are now preparing for a longer period of war than initially thought.

"We want to show maximum solidarity to Ukraine but it's clear the conflict is in the balance.

"We need to think, if this is going to last months, possibly years, how we keep supporting at the right pace the Ukrainian resistance.

"It's not just conventional warfare we see, we've also got cyber misinformation, we need to adapt.

"We can't allow his [Putin's] bullying behaviour, whether it's economic warfare or military warfare, to succeed".

Raab is echoing UK Foreign Secretary Liz Truss' warning that the West must be prepared "for the long haul".

"We will never feel safe again. So we must be prepared for the long haul and double down on our support to Ukraine," she is expected to say in a speech later today.

Despite the grim news, UK's Ministry of Defence said overnight that Ukraine retains control over the majority of its airspace and that Russia has failed to effectively destroy the Ukrainian Air Force or suppress Ukrainian air defences.

"Ukraine continues to hold Russian air assets at risk."

Russian air activity is primarily focused on southern and eastern Ukraine, providing support to Russian ground forces.

Russia has limited air access to the north and west of Ukraine, limiting offensive actions to deep strikes with stand-off weapons.

Meanwhile, the Russian foreign ministry said Wednesday that it has banned entry to 287 British MPs after the UK black-listed Russian politicians over Moscow's military operation in Ukraine.

"In response to the decision taken by the British government on March 11 to add 386 State Duma deputies to a sanctions list, in a reciprocal move, personal restrictions are being placed on 287 members of the House of Commons," the ministry said in a statement.

It said that the MPs are barred from entering the country from now on.

The House of Commons has a total of 650 members.

Moscow said the list is made up of MPs who have played "the most active part" in drawing up anti-Russian sanctions and contributed to "Russophobic hysteria".

Among those black-listed are Speaker Lindsay Hoyle as well as Cabinet members including Minister for Brexit Jacob Rees-Mogg and Environment Secretary George Eustice.

The list also includes Labour MPs, among them Diane Abbott, a close ally of former party leader Jeremy Corbyn.

British Prime Minister Boris Johnson said in parliament that those included in the list "should regard it as a badge of honour".

"What we will do is keep up our robust and principled support for the Ukrainian people, and their right to protect their lives, their families, and to defend themselves.

"That is what this country is doing, and that has the overwhelming support, I think, of the whole House."

Russia has already black-listed Johnson as well as Raab, Foreign Secretary Liz Truss, Defence Secretary Ben Wallace and several others.

Russia's foreign ministry on Wednesday also announced the expulsion of three Norwegian diplomats in a tit-for-tat measure after Oslo expelled three Russian diplomats earlier this month