He made the comments just after meeting with President Joe Biden at the White House. "We just have to be prepared for the long haul," Stoltenberg said, adding ominously, "Because what we see is that this war has now become a war of attrition."

The NATO chief emphasized that Ukrainians are "paying a high price for defending their own country on the battlefield, but also we see that Russia is taking high casualties."

"Most wars - also, most likely this war - will at some stage end at the negotiating table, but what we know is that what happens around the negotiating table is very closely linked to the situation on the ground, on the battlefield," he explained.

Thus far a handful of European countries have urged robust negotiations, particularly France under Macron, with Italy last month also offering a detailed peace plan; however, the Ukrainian and Russian sides have ceased meeting since prior Turkey-hosted talks failed to make any significant progress.

US and UK leaders in particular seem to have urged Zelensky to fight on and not be willing to make any territorial concessions. Some reports have even dubbed Biden and the UK's Johnson the "primary obstacles to peace" in Ukraine as others like Macron hold regular talks with Putin, hoping for some kind of breakthrough. Some pundits have said more cynically that the West stands ready to "fight till the last Ukrainian".