By Andreas Rinke and Tom Balmforth
BERLIN/KYIV (Reuters) -The United States and Germany were poised on Wednesday to announce plans to deliver heavy tanks to Ukraine, sources said, a decisive boost in support hailed in Kyiv as a potential breakthrough and condemned by Moscow as a reckless provocation.
Kyiv has been calling for months for Western main battle tanks that would give its forces the firepower, protection and mobility to break through Russian defensive lines and swoop through territory occupied by the invaders.
"A few hundred tanks for our tank crews .... This is what is going to become a real punching fist of democracy," Andriy Yermak, the head of Ukrainian President Volodymyr Zelenskiy's administration, wrote on Telegram as reports of the plans emerged.
While there was no official confirmation, the expected delivery of dozens of U.S. M1 Abrams tanks and at least one company of 14 German Leopards would mark a watershed in Western support for Ukraine. Germany's decision would open the door for other European allies that also field Leopards to send them too. Kyiv wants hundreds.
Just last week, allies pledged billions of dollars' worth of fresh military aid but stopped short of sending the tanks, with some politicians in Germany wary of provoking Moscow to escalate.
Zelenskiy, who turned 45 on Wednesday, again pressed Western allies to provide their most modern battle tanks, saying "the need is larger" in his nightly video address on Tuesday.
Moscow says supplies of modern offensive weaponry to Ukraine only postpone what it sees as an inevitable Russian victory. Anatoly Antonov, Russia's ambassador in Washington, said deliveries of U.S. battle tanks would be a "another blatant provocation".
"It is obvious that Washington is purposefully trying to inflict a strategic defeat on us," Antonov said on the embassy's Telegram messaging channel. "American tanks will be destroyed by our military in the same way all other samples of NATO equipment are being destroyed."
Western officials who support sending the tanks have dismissed Moscow's threats as bluster, arguing that Russia is already waging war at full tilt and has been deterred from attacking NATO.
DOZENS OF TANKS
In the 11 months since it invaded, Russia has killed thousands of civilians, forced millions from their homes and reduced entire cities to rubble.
It says its "special military operation" was necessary to halt a security threat arising from Ukraine's ties to the West, which it now portrays as seeking to destroy it. Kyiv and its Western allies say Ukraine never threatened Russia, and the invasion is a war of aggression to subdue its neighbour and seize land.
Ukraine defeated Russia's troops on the outskirts of Kyiv last year and later drove them out of swathes of occupied land. But Moscow still occupies around a sixth of Ukraine, which it has declared part of Russia.
The front line has been largely frozen in place for two months despite heavy losses on both sides, while both are believed to be planning new offensives for the spring.
Zelenskiy said that Russia was intensifying its push toward Bakhmut, an industrial town in eastern Ukraine where thousands of troops have been killed in months of trench battles that both sides refer to as a "meat grinder".
The Russian-installed governor of Ukraine's Donetsk region said on Wednesday that units of Russia's Wagner contract militia were now moving forward inside Bakhmut.
"Units, in particular Wagner, are advancing in Artyomovsk itself," TASS news agency quoted Denis Pushilin as saying, using the Russian name for Bakhmut. "Fighting is already taking place in the outskirts and in neighbourhoods that until very recently were held by the enemy."
Reuters could not verify the situation there.
Western military experts say Russia's focus on Bakhmut has made its forces vulnerable by squandering manpower on a costly battle for a target with limited strategic significance. But some argue that the slow pace of Western military aid so far has held Ukraine back from counterattacking.
Analysts at the Washington-based Institute for the Study of War said the West's slowness to provide more weaponry had "contributed to Ukraine's inability to take advantage of having pinned Russian forces in Bakhmut".
The question of whether to send heavy tanks has dominated debate among allies over how best to support Ukraine.
Germany has been pivotal because its Leopards, fielded by some 20 armies around the world, are available in much larger numbers than other European heavy tanks, and easier to deploy and maintain than the fuel-hungry turbine-powered U.S. Abrams.
But Berlin had been reluctant to send them unless Washington also sent its tanks to demonstrate a united Western front.
Two U.S. officials told Reuters on Tuesday that Washington was ready to start a process that would eventually send dozens of M1 Abrams tanks to Ukraine. In Germany, two sources said Chancellor Olaf Scholz had decided to send the Leopards and allow other countries such as Poland to do so as well.
(Reporting by Reuters bureaus; Writing by Cynthia Osterman and Stephen Coates; Editing by Himani Sarkar and Kevin Liffey)