The United States is expected to announce an additional 275 million US dollars (£216 million) in military aid for Ukraine as Kyiv struggles to hold off advances by Russian troops in the Kharkiv region, two US officials have said.

This will be the fourth instalment of military aid for Ukraine since Congress passed a long-delayed foreign aid bill late last month and comes as the Biden administration has pledged to keep weapons flowing regularly and to get them to the front lines as quickly as possible.

The package includes high-mobility artillery rocket systems, or HIMARS, as well 155mm and 105mm high-demand artillery rounds, according to the officials.

US defence secretary Lloyd Austin
US defence secretary Lloyd Austin said Ukraine was in a ‘moment of challenge’ (Mark Schiefelbein/AP)

It follows a monthly gathering on Monday of about 50 defence leaders from Europe and elsewhere who meet regularly to co-ordinate getting more military aid to Ukraine.

At this latest meeting, US defence secretary Lloyd Austin said Ukraine was in a “moment of challenge” due to Russia’s new onslaught on Kharkiv, Ukraine’s second-largest city.

He pledged to keep weapons moving “week after week.”

Russia has sought to take advantage of Ukrainian shortages in manpower and weapons while the war-torn country waits for the arrival of more US assistance, which was delayed for months in Congress.

Ukrainian forces have been pushed backwards in places, while Russia has pounded its power grid and civilian areas.

In the month since US president Joe Biden signed the 95 billion US dollars (£75 billion) foreign aid package, which included about 61 billion (£48 billion) for Ukraine, the US has announced and started to send almost 1.7 billion US dollars (£1.3 billion) in weapons pulled from Pentagon stockpiles.

It has also announced six billion (£4.7 billion) in funding through the Ukraine Security Assistance Initiative.

This pays for longer-term contracts with the defence industry and means that the weapons could take many months or years to arrive.

With this latest package, the US has now provided almost 51 billion (£40 billion) in military assistance to Ukraine since Russia invaded in February 2022.