The United States and its allies pledged new packages of ever heavier weapons for Ukraine during a meeting on Tuesday at a German air base, brushing off a threat from Moscow that their support for Kyiv could lead to nuclear war.
US officials have switched emphasis this week from speaking mainly about helping Ukraine defend itself to bolder talk of a Ukrainian victory that would weaken Russia's ability to threaten its neighbors.
One of President Vladimir Putin's closest allies, Nikolai Patrushev, said Ukraine was spiraling towards a collapse into "several states" due to what he cast as a US attempt to use Kyiv to undermine Russia. The comments seemed to be an effort to blame Washington for any break-up of Ukraine that emerges from the war, now in its third month.
U.SDefense Secretary Lloyd Austin, welcoming officials from more than 40 countries to Ramstein Air Base in Germany, headquarters of US air power in Europe, said: "Nations from around the world stand united in our resolve to support Ukraine in its fight against Russia's imperial aggression."
"Ukraine clearly believes that it can win, and so does everyone here."
The United States has ruled out sending its own or NATO forces to Ukraine but Washington and its European allies have supplied Kyiv with arms including howitzer heavy artillery, drones and anti-aircraft Stinger and anti-tank Javelin missiles.
In a notable shift, Germany, which had come under pressure after refusing Ukrainian pleas for heavy weapons, announced it would now send Gepard light tanks with anti-aircraft guns. Washington welcomed the move.
US officials, speaking on condition of anonymity, believe Russia will rely heavily on artillery strikes to pound Ukrainian positions while moving in ground forces from several directions to try to envelop and wipe out much of Ukraine's military.
But Washington also estimates that many Russian units are depleted, with some operating with personnel losses as high as 30% - a level considered by the US military to be too high to keep fighting indefinitely.
US officials cite anecdotes of Russian tanks with lone drivers and no crew, and substandard equipment that is either prone to breakdowns or out of date.
War by 'proxy'
In a marked escalation of Russian rhetoric, Foreign Minister Sergei Lavrov was asked on state TV late on Monday about the prospect of World War Three and whether the current situation could be compared to the 1962 Cuban missile crisis that nearly caused nuclear war.
"The danger is serious, real," Lavrov said, according to the ministry's transcript of the interview. "NATO, in essence, is engaged in a war with Russia through a proxy and is arming that proxy. War means war."
Pentagon spokesman John Kirby decried Lavrov's comments.
"It's obviously unhelpful... and certainly is not indicative of what a responsible (world power) ought to be doing in the public sphere," Kirby said. "A nuclear war cannot be won and it shouldn't be fought. There's no reason for the current conflict in Ukraine to get to that level at all."
Mark Milley, chairman of the US Joint Chiefs of Staff, told reporters while flying to Tuesday's meeting in Germany that the next few weeks in Ukraine would be "very, very critical".
"They need continued support in order to be successful on the battlefield," he said.
Ukraine's general staff said Russia's offensive continued in the eastern regions of Kharkiv and Donetsk, where it said they were taking "actions along almost the entire line of contact".
Russia is probably trying to encircle heavily fortified Ukrainian positions in the east, the British military said in an update on Tuesday, adding that forces were trying to advance towards the cities of Sloviansk and Kramatorsk.
In an interview with the government newspaper Rossiyskaya Gazeta, Putin ally Patrushev accused the United States of "trying to divide essentially a single people", echoing Putin's contention that Ukraine is really a historic part of Russia.
"The result of the policy of the West and the regime in Kyiv can only be the disintegration of Ukraine into several states," added Patrushev, who is secretary of Russia's Security Council.
United Nations Secretary-General Antonio Guterres, on a visit to Moscow on Tuesday, said he was ready to fully mobilize the organization's resources to save lives and evacuate people from the besieged Ukrainian city of Mariupol.
Guterres, who is also due to visit Kyiv, proposed a "Humanitarian Contact Group" of Russia, Ukraine and UN officials to seek opportunities "for the opening of safe corridors, with local cessations of hostilities, and to guarantee that they are actually effective".
Ukrainian Deputy Prime Minister Iryna Vereshchuk said no corridors were operating on Tuesday due to continued fighting.
A new source of concern is Transdniestria, a separatist region of Moldova just to the west of Ukraine, which has been occupied by Russian troops since the 1990s. Two radio masts there were destroyed by explosions early on Tuesday, following other blasts in Transdniestria on Monday.
The separatist authorities said they were raising their terrorism threat level to red, while the Kremlin said it was concerned. Russia's TASS news agency quoted the separatist leader as saying the attacks could be traced back to Ukraine.
Moldova's pro-Western President Maia Sandu blamed the "escalation attempts" on "pro-war" factions in Transdniestria.
Moldova expressed alarm last week after a top Russian general said Moscow aims to forge a path through Ukraine to Transdniestria, where he said Russian speakers needed protection from oppression. Moldova, an ex-Soviet state, has close cultural and linguistic ties to NATO member Romania.
Russia's two-month-old invasion of Ukraine has left thousands dead or injured, reduced towns and cities to rubble, and forced more than 5 million people to flee abroad.
Moscow calls its actions a "special operation" to disarm Ukraine and protect it from fascists. Ukraine and the West call this a false pretext for an unprovoked war to seize territory.