Antony Blinken says Ukraine war at 'critical' point as Putin's army offensive slowed near Kharkiv

America’s top diplomat Antony Blinken said Putin’s war in Ukraine was at a “critical” point as Russia forces were seeking to advance in the north east of the country.

The warning from the US Secretary of State came as Ukraine's top military spy said Kyiv's troops appeared close to stabilising the situation after Russia's ground attack into the Kharkiv region.

But Kyrylo Budanov warned of a build-up of Russian forces to the north near the Sumy region.

A cross-border attack on a new flank in Sumy region would likely stretch Kyiv's depleted defenders even further after Russia's incursion in the north of Kharkiv region opened a new front on Friday, forcing Ukraine to rush in reinforcements.

Russia has already made inroads into the north of Kharkiv region in two areas and said on Tuesday that it had taken a 10th border village, Buhruvatka.

Mr Budanov said Moscow had already committed all the troops it had in the border areas for the Kharkiv operation, but that it had other reserve forces that he expected to be used in the coming days.

"As of yesterday evening, a rapid trend towards a stabilisation of the situation had emerged - that is, the enemy is, in principle, already blocked at the lines that it was able to reach," he said in televised comments.

Top Ukrainian officials stressed that they do not believe Russia has the troop numbers to capture the city of Kharkiv.

Russia was maintaining the tempo of its attacks in the region, according to data compiled by the Ukrainian General Staff which said there had been 13 Russian assaults so far on Tuesday, compared with 13 on Monday and 22 the day before.

Mr Budanov described the situation as fluid and rapidly changing, saying the "active phase" of the Russian operation was still under way.

Defence experts said Putin’s military is blowing up bridges as it appears to be creating a “buffer zone” to limit attacks into Russia rather than advancing on Ukraine’s second largest city.

They stressed that Russian forces had made “tactically significant advances” towards Kharkiv in the north east of the country.

But they are not picking up signs yet that Putin’s army chiefs are planning a deep offensive towards the city of Kharkiv.

Mr Blinken visited Kyiv on Tuesday, in a show of support for Ukraine, as the first batch of a huge new package of military aid from America was arriving in the country.

"We know this is a challenging time," Blinken said in the Ukrainian capital where he met with Ukraine’s leader Volodymyr Zelensky. But he added that American military aid is "going to make a real difference against the ongoing Russian aggression on the battlefield.”

The weapons provided were said to include artillery, missile interceptors, and long-range precision missiles capable of striking targets more than 200 miles away.

F-16 fighters jets being supplied by the West are expected to arrive in Ukraine in June or July.

But Putin’s army has been on the advance in recent months, as the additional military support was delayed, particularly by a group of pro-Trump Republicans in Washington.

“Russian forces continued to make tactically significant advances north and northeast of Kharkiv City on May 13 and currently appear to be prioritizing the rapid establishment of a ‘buffer zone’ along the international border over setting conditions for deeper penetrations into northern Kharkiv Oblast (province),” said the Institute for The Study of War.

Putin’s army has seized a number of, or at least parts of, villages and towns in the area in recent days, though Ukraine sources claimed Russian units had suffered heavy losses.

The ISW added: “Russian forces’ relatively rapid rate of advances in Vovchansk and their reported destruction of several bridges across key waterways within the settlement suggest that Russian forces are prioritizing the creation of a ‘buffer zone’ over a deeper penetration.”

The Washington-based military think tank explained further: “Russian forces notably conducted strikes against bridges over the Vovcha River immediately west and east of Vovchansk on May 12 and began targeting bridges over the river and logistics lines in Vovchansk itself on May 13, reportedly only leaving Ukrainian forces with two usable bridges over the Vovcha in Vovchansk.

“It is unclear why Russian forces would largely target bridges they would need to cross and ensure stable logistics across the Vovcha River for offensive operations deeper into northern Kharkiv Oblast, so these strikes suggest that Russian forces may be prioritizing immediate gains in an unfortified area of northern Ukraine.”

Tanks were said to have been used in the advance on Vovchansk on Sunday night, with attacks continuing on Monday.

The ISW stressed: “The deployment of armoured assets in this area suggests that Russian forces are seeking to make rapid gains, but they do not appear to be setting conditions at this time for such gains to be on the southern side of the Vovcha River deeper into northern Kharkiv Oblast.

“These indicators collectively suggest that Russian forces are likely trying to create the promised ‘buffer zone’ in the border area instead of pursuing deeper gains into Kharkiv Oblast or towards Kharkiv City.”

Mr Blinken’s visit comes less than a month after Congress approved a long-delayed foreign assistance package that sets aside £48 billion in aid for Ukraine, much of which will go toward replenishing badly depleted artillery and air defense systems.

On his fourth trip to Kyiv since Russia invaded Ukraine in February 2022, America’s top diplomat stressed the Biden administration's commitment to Ukraine's defence and long-term security, US officials said.

They noted that since President Joe Biden signed the aid package late last month, the administration has already announced $1.4 billion (£1.1 billion) in short-term military assistance and $6 billion (£4.8 billion) in longer-term support.

It is "trying to really accelerate the tempo" of U.S. weapon shipments to Ukraine, national security adviser Jake Sullivan said.

"What I am going to suggest is that the level of intensity being exhibited right now in terms of moving stuff is at a 10 out of 10," Mr Sullivan said at a White House briefing Monday.