Experts have warned that Russian President Vladimir Putin may be preparing to launch an all-out offensive against Ukraine’s second city.

With U.S. military aid stalled, Ukraine is struggling to obtain enough ammunition and soldiers to continue its defense against Russia — which could open the door to a push toward Kharkov.

Orysia Lutsevych, director of the Ukraine Forum, a think tank at Chatham House in London I Russia may be preparing a ground attack on the city, which it has struck in recent months using glide bombs and S-300 ballistic missiles.

She said Ukraine was just “patching the quilt and hoping to avoid disaster,” while warning that might not be enough. Ukraine is struggling to acquire enough artillery shells and anti-aircraft weapons that are crucial to defending critical infrastructure such as cities and nuclear power plants and maintaining a 1,200-kilometer frontline.

Lucevich said any attack on Kharkov would be “in line with Russia’s war objectives” and could be similar to the scorched earth offensive against Mariupol in 2022. She added that this could lead to a “humanitarian disaster”.

According to recent estimates, approximately one million people currently live in Kharkiv.

Western officials familiar with Ukraine’s military told Bloomberg Ukraine is at its most vulnerable period Since the war broke out more than two years ago, there are fears its military is close to collapse.

They said Moscow could see significant progress for the first time since the conflict began.

Kharkiv has been subject to heavy Russian bombing in recent months, with Russian news media raising the possibility of an attack on the city close to the border.

Ms. Lutsevich predicted that no ground attack would occur before late summer or early autumn because Russia currently does not have enough troops to attack a city of that size.

“Aerial bombardment with drones is one thing, but seizing territory is another,” she said. “To seize territory, they need larger infantry units, brigades and motorized units that will actually seize territory.”

She said this opened up opportunities for increased Western support for Ukraine.

Russia has also been attacking Ukraine’s energy bases and this week destroyed the Kiev region’s largest thermal generator, Tripilska. Rutsevich said this represents a shift in Russia’s goals as it seeks to make it more difficult for the West to sustain Ukraine’s economy.

It has previously attacked Ukraine’s energy distribution system, which she said is easier to replace. She claimed that repairing the generators could take six months, a blow to private companies seeking to export goods as well as civilians and meaning more financial support from the West is needed.

“This is another way to make bailing out Ukraine expensive for Western countries,” she said. “They want to eliminate Ukraine’s self-sufficiency income and make it unaffordable for the West.”

Earlier this week, analysts said Russia was in danger of slowing down due to a surge in equipment losses, a situation they called “unsustainable.”

Russian troops laid siege to Mariupol for months, sealing off the Azovstal steel plant and hiding fighters and civilians inside.