Russian Foreign Minister Sergey Lavrov has said Moscow and Washington are “in a hot phase of the war” over US supplies of weapons to Ukraine.
Moscow must maintain relations with the US, Mr Lavrov told state television.
Russia had not yet lost hope that the US would “wake up to reason (and) will resume some kind of dialogue”, he said on Wednesday.
“We are really in a hot phase of a war because Ukrainian Nazis are fighting mostly with US weapons,” Mr Lavrov said in the comments that were posted to Telegram by reporter Pavel Zarubin.
Mr Lavrov said the US administration “each time threatens to supply systems that have an ever-greater range and deadliness” to Ukraine.
“At least, we do not lose hope that the minds of the Americans will wake up, and they will resume some kind of dialogue. We’ll see, we don’t have long to wait,” Mr Lavrov said.
Separately on Wednesday, Russian President Vladimir Putin told the new US and EU ambassadors that their countries were responsible for a deterioration in relations since Russia sent its armed forces into Ukraine last year.
The ambassadors were among 17 who presented their diplomatic credentials to Mr Putin at a televised ceremony in the Kremlin.
Mr Putin told new US Ambassador Lynne Tracy that US support for a revolution in Ukraine in 2014 had led to the Russia-Ukraine conflict.
He said relations were in “a deep crisis” that was “based on fundamentally different approaches to the formation of the modern world order”.
“Dear Madam Ambassador, I know you may not agree, but I cannot but say that the United States' use … of such tools as support for the so-called 'colour revolutions', support in this regard for the coup in Kyiv in 2014, ultimately led to today's Ukrainian crisis,” Mr Putin said.
Mr Putin then told new EU ambassador Roland Galharague that the body “initiated a geopolitical confrontation with Russia”.
Nikolai Patrushev, chair of Russia's Security Council, told Tass news agency that “with the assistance of the US and its allies, Kiev is intensifying its terrorist activity” in four regions of Ukraine that Moscow said last year it was formally annexing.
Russia said it was forced to intervene in Ukraine to halt Western interference that was becoming a threat to its security.
The West and Kyiv dismissed this as a baseless pretext for a war of conquest.
Germany and UK deliver tanks to Ukraine
Ukrainian President Volodymyr Zelenskyy said Poland would to help form a coalition of Western powers to supply warplanes to Kyiv, as his fighters continued to defend their eastern bastion of Bakhmut in the face of relentless Russian assaults.
During a visit to Warsaw on Wednesday, Mr Zelenskiyy said Poland had been instrumental in getting Western allies to send battle tanks to Ukraine and he believed it could play the same role in a “planes coalition”.
The Polish government said it would send 10 more MiG fighter jets on top of four provided earlier, but so far there has been no agreement from the US or Ukraine's other major military backers to send the F-16 fighters Kyiv has requested.
Russia 'does not control' Bakhmut
On the front lines, Mr Zelenskyy said Ukrainian troops faced a difficult situation in the battle for Bakhmut and the military would take “corresponding” decisions to protect them if they risked being encircled by Russian forces.
“We are in Bakhmut and the enemy does not control it,” Mr Zelenskyy said, refuting claims by Russian forces that they had captured the city, in ruins after months of attritional warfare and bombardment.
“For me, the most important is not to lose our soldiers and of course if there is a moment of even hotter events and the danger we could lose our personnel because of encirclement — of course the corresponding correct decisions will be taken by generals there,” Mr Zelenskiyy said, apparently referring to withdrawal.
The battle for Bakhmut, one of the last urban centres yet to fall to Russia in eastern Donetsk province, has proven one of the bloodiest of Russia's invasion, now in its 14th month.
Ukrainian military commanders have stressed the importance of holding Bakhmut and other cities and inflicting losses on Russian troops before an anticipated counter-offensive against them in the coming weeks or months.
“Bakhmut is performing the key task of inflicting as many losses on Russia as possible and, most importantly, to prepare for a counter-attack to take place in late April-May,” military analyst Pavel Narozhniy told NV Radio in Ukraine.
The US-based Institute for the Study of War said mercenaries from Russia's Wagner private militia were likely to continue trying to consolidate control of the city centre and push westward through dense urban neighbourhoods.
