"For Ukraine to win this war -- and to accelerate that day -- they must gain a decisive advantage on the battlefield... Instead of an incremental approach, we need to move faster on artillery, armour, and air defence," he is expected to say in a virtual meeting a year on from Russia's invasion.

The UK is due to hold a minute's silence at 11:00 am (1100 GMT) to mark the first anniversary of the conflict.

Sunak will join military personnel in observing the national moment of reflection at his Downing Street office, a statement said.

Alongside the Ukrainian ambassador to the UK, Vadym Prystaiko, he will also host Ukrainian armed forces personnel and representatives of 10 nations supporting the government's programme to provide them with extra military training.

Sunak and his wife, Akshata Murty, will also hang a blue and yellow wreath on the door to his office at No 10 Downing Street, the statement added.

"As we mark one year since a full-scale war broke out on our continent, I urge everyone to reflect on the courage and bravery of our Ukrainian friends who, every hour since, have fought heroically for their country," he said in the statement.

"I am proud that the UK has stood shoulder-to-shoulder with Ukraine through this horrific conflict."

In his comments to G7 allies, Sunak is expected to add that while the coming weeks will be difficult for Ukraine, they will also be hard for Russia.

"They are over-reaching once again. So now is the time to support Ukraine's plan to re-arm, regroup, and push forward," he will say.

After the US, the UK has been the biggest donor of aid to Ukraine.

It was the first to pledge heavy tanks to Kyiv but has so far resisted sending fighter jets.