Ukrainian President Volodymyr Zelensky called for heavy weapons from the West and praised Britain for already deciding to send them.
Western countries have produced a steady supply of weapons to Ukraine since Russian forces invaded on Feb 24, 2022, but Zelensky and his government are insisting they need tanks.
"A new defence aid package has been announced - exactly what is needed: main battle tanks, other armoured vehicles and artillery," Zelensky said in his daily video address on Monday evening.
Britain confirmed on Monday it was going to send 14 Challenger 2 tanks and other hardware, including hundreds more armoured vehicles and advanced air defence missiles. Britain would be the first Western country to supply the heavy tanks Kyiv has been calling for.
Germany is under pressure to send Leopard 2 tanks to Ukraine, but its government says such tanks should be supplied only if there is agreement among Kyiv's main allies, particularly the United States.
The German-made tank is regarded as one of the West's best. Countries operating the Leopard include Canada, Denmark, Finland, the Netherlands, Norway, Austria, Poland, Spain, Sweden and Turkey.
The US operates thousands of M1 Abrams tanks built by General Dynamics, but they are seen as unsuitable for Ukraine as they are driven by gas turbine engines.
Until now, Ukraine has relied primarily on Soviet-era T-72 tank variants.
Zelensky said he expected decisions on further arms deliveries from the World Economic Forum in Davos, which officially got started on Monday, and the Ukraine Contact Group conference in Ramstein, due to meet on Friday at the US airbase in Germany.
Western officials want to strike a balance between ensuring Ukraine can defend itself and not supplying arms that could encourage Kyiv to make attacks on Russia or draw the North Atlantic Treaty Organization (Nato) into conflict with Moscow.
Some Western officials have flagged another concern - that Russia, or even China, might get its hands on advanced Western weaponry deployed in Ukraine, enabling Moscow or Beijing to steal Western military technology.
Oleskiy Danylov, Secretary of Ukraine's Security Council, also mentioned the need for an acceleration in weapons supplies because the government expected Russia "to attempt to make a so-called final push".
Danylov told Ukrainian television that could take place on the invasion's anniversary or in March.
"We must prepare for such events every day. And we are preparing … The first and last question is always about weapons, aid to help us defeat this aggressor that invaded our country," Danylov said.
The Kremlin said on Monday that tanks Britain plans to send to Ukraine "will burn", warning the West that supplying a new round of more advanced weapons to Ukraine would not change the outcome of the war.
"They are using this country as a tool to achieve their anti-Russian goals," Kremlin spokesman Dmitry Peskov said when asked about the British tanks.
"These tanks are burning and will burn just like the rest," Peskov said.
Russia's President Vladimir Putin said in an interview aired on Sunday that the military operation in Ukraine had gained positive momentum and that he hoped his soldiers would deliver more wins after Russia claimed control of the eastern Ukrainian salt-mining town of Soledar.
The Kremlin chief now casts the war in Ukraine as an existential battle with an aggressive and arrogant West and has said that Russia will use all available means to protect itself and its people against any enemy.
Vladimir Solovyev, a pro-Kremlin presenter on Rossiya 1 state television, said any Western countries which supplied more advanced weapons to Ukraine should be considered legitimate targets for Russia.
"De facto, Britain has entered the war," Solovyev told his flagship Sunday night talk show on state television. "I consider Britain is now a legitimate target for us."
His comments were followed by a discussion on state television with lawmaker Andrei Gurulyev about the utility of resuming Russia nuclear testing so that the whole world "shuddered", and even of wiping out Britain.
"If there is no London, then we would have victory," Gurulyev said. "On Britain, I said six months ago that it should be wiped from the face of the Earth."
Meanwhile in Berlin, German Chancellor Olaf Scholz said he would "soon" name a successor to Christine Lambrecht, who resigned as the country's defence minister on Monday.
Lambrecht's resignation followed a series of missteps and was a blow to Scholz's government as it weighs crucial decisions on arming Ukraine, namely the Leopard 2 tanks.
Germany has given Ukraine substantial support in recent months, including howitzers, Gepard self-propelled anti-aircraft guns and the first of four IRIS-T surface-to-air missile systems.
Earlier this month, Germany agreed to provide 40 Marder armoured personnel carriers and a Patriot air defence missile battery to Kyiv.
But critics, some inside Germany's governing coalition, have long complained of Scholz's perceived hesitancy to step up aid. Lambrecht was overshadowed on the issue by the chancellor, who made most major announcements.
Britain on Monday urged Germany to permit the supply of Leopard tanks to Ukraine, stressing that it could unlock support from other nations and Berlin would not be acting alone if it supplied its own tanks.
"It has been reported that obviously Poland is very keen to donate some Leopards, as is Finland," British defence minister Ben Wallace told parliament.
"All of this currently relies on the German government's decisions - not only whether the Germans will supply their own Leopards, but whether or not they'll give permissions to others. I would urge my German colleagues to do that."
