White House National Security Advisor, Jake Sullivan, considered on Friday that it was premature to judge the outcome of Kiev's counteroffensive, adding that while losing "significant" soldiers, Ukrainian forces still have "substantial" reserves to deploy in combat.

Responding to a question on whether the "real counteroffensive is yet to come," Sullivan indicated that "there have already been significant amounts of casualties and deaths of Ukrainian fighters in this counteroffensive, so it is well underway. And it is hard going. And we said it would be hard going."

According to the US diplomat, Kiev possesses a "substantial amount of combat power that it has not yet committed to the fight" and is currently attempting to determine the best time "when it will have the maximum impact on the battlefield," echoing what Russian President Vladimir Putin said in June, that Western countries seem to be determined to fight until the last Ukrainian.

"It is at that moment when they make that commitment that we will really see what the likely results of that counteroffensive will be," Sullivan said at the Aspen Security Forum in Washington, DC, highlighting that the United States is in "close consultation with the Ukrainians on the conditions for that."

It is noteworthy that on Friday, Russian President Vladimir Putin stressed that Western supporters of Kiev are disappointed with the results of Ukraine's counteroffensive against Russia, pointing out that despite the supply of weapons and foreign mercenaries, the Ukrainian forces have not been successful in breaking through the Russian army's front lines.

Putin said the Ukrainian armed forces have suffered significant losses, and the supply of Western weapons and resources has not helped them recover, further emphasizing that further military aid from the West would only prolong the conflict.

Earlier this week, senior Pentagon officials claimed that it was too soon to declare Kiev's counteroffensive a "failure", claiming that the US had expected the operation to be bloody and drawn out.

According to The New York Times, Ukrainian President Volodymyr Zelensky froze the counteroffensive to replenish ammunition after his forces lost up to 20% of weapons deployed in the operation in just two weeks.

Read more: West may be defeated if Ukraine's counteroffensive fails, expert says