Chairman of the Joint Chiefs of Staff Gen. Mark Milley gives a thumbs up as he leaves the podium following a press briefing with Chairman of the Joint Chiefs of Staff Gen. Mark Milley at the Pentagon on Thursday, May 25, 2023 in Washington. AP
His comments underlined forecasts that the war in Ukraine is set to drag on, with neither side positioned to win a clear-cut victory and no negotiations currently taking place.
"This war, militarily, is not going to be won by Russia. It's just not," Milley told journalists after the conclusion of a virtual meeting of dozens of countries that support Ukraine.
Russia's original strategic objectives, including overthrowing the government in Kyiv, "are not achievable militarily, they're not going to be done," Milley said.
At the same time, there are hundreds of thousands of Russian soldiers in Ukraine, making Kyiv's objective of recapturing all of its territory unlikely "in the near term," he said.
"That means fighting is going to continue, it's going to be bloody, it's going to be hard. And at some point, both sides will either negotiate a settlement or they'll come to a military conclusion."
The United States has spearheaded the push for international support for Ukraine, quickly forging a coalition to back Kyiv after Russia invaded in February 2022 and coordinating aid from dozens of countries.
In total, Ukraine's supporters have provided nearly $65 billion in security assistance to the country, US Defense Secretary Lloyd Austin said.
The White House said last week that Washington would support providing advanced warplanes including F-16s to Ukraine, dropping previous reluctance to do so.
On Thursday, Kyiv's supporters "discussed plans for training Ukrainian pilots on fourth-generation fighter aircraft, including the F-16," Austin said alongside Milley, noting that "planning and executing this training will be a significant undertaking."
The US defense chief said that a fund may be established for financial contributions to aid the effort from countries that do not have F-16s or the capabilities to assist directly with training, maintenance or sustainment.
Milley explained the US shift in favor of providing Kyiv with the warplanes by saying that doing so earlier in the conflict would have taken funds away from more immediate needs, while building Ukraine's air force is a long-term endeavor.
"It's going to take a considerable length of time to build up an air force that's the size and scope and scale that'll be necessary," he said.