Based on the current situation on the battlefield, Western officials are beginning to see it as unlikely that a major success for Ukraine's Defence Forces would make a major difference.

CNN sources, four high-ranking officials from the United States and other Western countries, doubt that the Ukrainian Armed Forces will be able to achieve great success, although they admit that there will be some progress in the coming weeks.

"But for them to really make progress that would change the balance of this conflict, I think, it’s extremely, highly unlikely," a senior Western diplomat told CNN.

"Our briefings are sobering. We’re reminded of the challenges they face. This is the most difficult time of the war," said Mike Quigley, an Illinois Democrat who recently returned from meetings in Europe with US commanders training the Ukrainians.

In particular, such challenges are the defensive lines that the Russians have managed to prepare, with a wide network of trenches and continuous mining. Ukraine has supposedly suffered "staggering losses" there, forcing the command to send some units back to regroup. CNN did not specify where this assessment came from.

One of the sources said that at the time of the interview, the Ukrainian military had not yet broken through the first line of defence. "Even if they would keep on fighting for the next several weeks, if they haven’t been able to make more breakthroughs throughout these last seven, eight weeks, what is the likelihood that they will suddenly, with more depleted forces, make them? Because the conditions are so hard," the source said.

One US official commented to journalists that Washington is aware of the level of difficulties faced by Ukrainian defenders and is less pessimistic.

"We all recognise this is going harder and slower than anyone would like – including the Ukrainians – but we still believe there’s time and space for them to be able to make progress," this official said.

John Kirby, Coordinator for Strategic Communications at the National Security Council in the White House, said in a comment that official Kyiv recognises the difficulties, but attempts are ongoing. "There is active fighting along that front, they are definitely trying to push forward. How far they’ll get, where that will be, what kind of breakthrough they might be able to achieve, I don’t think anybody can say right now. We’ve got to make sure we’re staying behind them and supporting them," Kirby said.

Many sources noted that the approaching autumn and worse weather conditions are leaving Ukraine with a limited window of time to develop an offensive.

Western officials also say that the difficulties in the offensive have revealed problems with the transformation of Ukrainian forces into combined arms units, which have sometimes taken eight weeks to learn how to use new Western weapons. One US source said that one of the reasons for Ukraine's more frequent attacks deep into Russian territory is an attempt to show Russia's vulnerability amid a lack of success on the battlefield.

Some sources described the initial expectations from Ukraine's counteroffensive as unrealistic and noted that they were now playing against Ukraine and increasing pressure from "some in the West" to begin peace talks, even with territorial concessions.

Some expressed concern that as disappointment with the contrast between high expectations and results grows, a "blame game" within Ukraine and among its allies will begin and weaken unity.

At the end of July, Pentagon Head Lloyd Austin said that Ukraine still had enough capacity to continue its counteroffensive.