For this year, it would be "very, very difficult" to militarily eject the Russian forces from every inch of territory that they have occupied in Ukraine, a top American general said.
That does not mean it cannot and will not happen, General Mark Milley, chairman of the US Joint Chiefs of Staff, said on Friday.
"From a military standpoint, I still maintain that for this year it would be very, very difficult to militarily eject the Russian forces from every inch of Ukraine and occupied or Russian-occupied Ukraine," General Milley told reporters at a news conference in Germany.
"That doesn't mean it can't happen, doesn't mean it won't happen, but it would be very, very difficult. I think what can happen is a continued defence stabilised in the front," he said.
Depending on the delivery of US equipment and training of the Ukrainian military, it is very possible for the Ukrainians to run a significant tactical or even operational-level offensive operation to liberate as much Ukrainian territory as possible, General Milley said.
"Then we'll see where it goes," he added.
The United States on Thursday announced another military assistance package of USD 2.5 billion for Ukraine to fight against Russian aggression, taking the total US military assistance to USD 27.5 billion.
This assistance package will provide Ukraine with hundreds of additional armoured vehicles, including Stryker armoured personnel carriers, Bradley infantry fighting vehicles, Mine-Resistant Ambush Protected vehicles, and High Mobility Multipurpose Wheeled vehicles, according to an official statement.
The package also includes critical additional air defence support for Ukraine, including more Avenger air defence systems, and surface-to-air missiles, as well as additional munitions for NASAMS that the US has previously provided.
General Milley said the Ukraine-Russia war, like many wars in the past, "will end at some sort of a negotiating table".
Russian President Vladimir Putin could end this war today, he said.
"He started it... he could end it today because it's turning into an absolute catastrophe for Russia -- massive number of casualties and lots of other damage to the Russian military," he said.
General Milley and US Defence Secretary Lloyd Austin addressed a joint news conference in Germany following the conclusion of the eighth Ukraine Defence Contact Group meeting that comprises defence leaders from more than 50 countries.
"As Russia's cruelty deepens, the resolve of this contact group grows, and that's clear from the announcements that we've heard today," Austin said.
"Several countries have come forward with key donations that will help protect Ukraine's skies and cities and citizens, and France and Germany and the UK have all donated air defence systems to Ukraine, and that includes a Patriot battery from Germany," he said.
Austin said the members of the Ukraine Defence Contact Group are standing up for a world where rules and rights matter, sovereignty is respected and people can choose their own path, free from tyranny and aggression.
"We will continue to build momentum, we'll support Ukraine against the Russian aggression for the long haul and we'll continue to work towards a free and secure Ukraine and a stable and decent world," he told reporters.
At the White House, NSC Coordinator for Strategic Communications John Kirby alleged that a Russian private military company, Wagner, is committing atrocities and human rights abuses in Ukraine and elsewhere around the world.
"Now, as his military continues to struggle in Ukraine, President Putin is increasingly turning to Wagner, which is owned by Yevgeniy Prigozhin, for military support. We are seeing indications, including in intelligence, that tensions between Wagner and the Russian Ministry of Defence are increasing," Kirby said.
"Wagner is becoming a rival power centre to the Russian military and other Russian ministries. Publicly, Prigozhin and his fighters have criticised Russian generals and defence officials for their performance on the battlefield," he said.
According to US assessment, Wagner currently has approximately 50,000 personnel deployed in Ukraine, including 10,000 contractors and 40,000 convicts, Kirby said as the White House announced a series of sanctions against it, including designating the company as a significant Transnational Criminal Organisation.