Ukraine has said it expects the West will send long-range missiles capable of striking almost 200 miles behind Russian lines.
The sophisticated weapons systems would be used to target Russia’s fragile supply chains, hitting ammunition depots, warehouses and other infrastructure critical to supporting its invasion.
It came after Washington announced it would send 31 M1 Abrams tanks and Germany committed to sending Leopard 2 tanks, also allowing other allies to send German-made ones in their possession.
The White House has previously denied Kyiv's requests for ATACMS, surface-to-surface missiles with a range of up to 190 miles.
But Mikhailo Podolyak, adviser to Ukrainian president Volodymyr Zelensky, said there was already "an understanding" in the West that fears of the missiles leading to escalation were misplaced.
He told The Telegraph: "Right now we are seeing a sharp change in sentiment among the political elites of European countries, who understand that we need to transfer all equipment, including armoured vehicles. And we will reach, I am sure, no doubt, an agreement on long-range missiles."
Ukrainian forces are currently equipped with Guided Multiple Launch Rocket Systems, a missile with a maximum range of around 50 miles when fired from a US Himars rocket launcher.
Mr Podolyak said the longer range missiles would be "part of the negotiation process" in the next arms packages for Ukraine.
He said: "Only these missiles will make it possible to destroy almost the entire infrastructure of the Russian rear army, and without it, they will fight much worse, if at all."
Britain, the first ally to provide tanks, has “not ruled out” sending longer-range precision missiles to Ukraine, but sources cautioned it was not being “considered” currently.
Meanwhile, Joe Biden on Wednesday night denied he had been forced into sending tanks by pressure from Berlin. Germany had refused to send its Leopard 2s unless the US sent some of its Abrams.
'Putin expected our support for Ukraine to crumble'
Mr Biden said: "Germany did not force me to change my mind. We wanted to make sure we were all together. That's what this is about, helping Ukraine defend and protect Ukrainian land. It is not an offensive threat to Russia."
Mr Biden said he had consulted with allies including Rishi Sunak, who he clumsily referred to as "Prime Minister Sunook".
He added: "Putin expected Europe and the United States to weaken our resolve. He expected our support for Ukraine to crumble with time. He was wrong."
The US president said he was "grateful" to his "close friend" Olaf Scholz, the German chancellor, adding: "Germany has really stepped up."
Mr Biden said delivering the Abrams tanks was "going to take time" but training for Ukrainian troops on them would begin "as soon as possible".
Retired general Mark Hertling, a former commander of US ground forces in Europe, estimated it would take "six to eight months" for the Abrams tanks to get to the battlefield.
Meanwhile, Mr Scholz insisted he had been "right" to delay approving deliveries of the Leopard tanks despite weeks of international pressure.
Germany will now provide 14 Leopards as a first step, and will also give European allies permission to re-export their German-made tanks to Ukraine.
The chancellor said the goal was to donate two battalions, about 80 tanks, to Kyiv in total. Ukraine first asked for tanks soon after Russia’s illegal invasion nearly a year ago.
Addressing the German parliament, Mr Scholz said: "I need to explicitly say it was right, and it keeps on being right, to not have been pushed forward, but to have waited for international cooperation to take place. It is correct to never go it alone.
"It's not far away from Berlin that a war on a big country is taking place. We want to avoid an escalation of this war so that it doesn't become a war between Russia and Nato.”
Mr Zelensky said he was “sincerely grateful to the chancellor” for his “important and timely decisions”.
Norway, the Netherlands and Spain said they were poised to join Poland, Finland and Portugal in committing Leopards from their armies to Ukraine’s cause. Denmark and Sweden are also considering sending tanks to Ukraine.
In the wake of the tank decisions, attention also turned to whether aircraft could be sent to Ukraine. Ukraine's deputy foreign minister called for the donation of F-16 and F-35 fighter jets.
Andriy Melnyk wrote on Twitter: "Dear allies, let's establish a powerful fighter jet coalition for Ukraine, with F-16, F-35, Eurofighter, Tornado, Rafale and Gripen jets."
But officials in Kyiv are not expected to make a significant push for combat aircraft, with long-range missiles now considered the priority.
Mr Scholz ruled out the prospect of providing Kyiv with F-16s.
RAF sources told The Telegraph that sending in aircraft "was seen as being too escalatory".
A source said: "Ukraine flies former Russian aircraft so to train on a Typhoon would likely take years. The only option would be for nations with former Russian aircraft to offer such aircraft, such as Poland."