Downing Street has said Britain will not dictate to allies what form support for Ukraine should take, amid pressure on Germany to step up its response.
Ukraine is asking for tanks and more powerful arms as Russia's war drags on, with Germany being urged to approve the transfer of Leopard 2 battle tanks which are made in the country.
NATO Secretary General Jens Stoltenberg called for the speedy delivery of new weapons to Ukraine on Tuesday.
After talks with German defence minister Boris Pistorius in Berlin, Stoltenberg said: "At this crucial moment in the war, we need to provide Ukraine with heavier and more advanced systems, and we need to do it faster."
The prime minister's official spokesman said the government will not "dictate to other countries exactly what they should or should not provide – first and foremost that must be for those countries."
He added: "We look to work with our allies in lockstep as much as possible.
"Our approach has borne fruit.
"You've seen the huge amounts of equipment, material and financial support that has been provided to Ukraine since the start of the war."
The government confirmed plans earlier this month to supply Kyiv with British Army Challenger 2 main battle tanks.
Poland has officially requested permission from Germany to transfer its Leopard 2 tanks to Ukraine to help fight Russia's invasion, the Polish defence minister has said.
German Foreign Minister Annalena Baerbock said on Sunday that Berlin would not seek to stop Poland providing the hi-tech armour to Kyiv.
Downing Street said there is "concerted and long-lasting" backing for Ukraine among allies.
Writing in the Daily Mail on Tuesday, former prime minister Boris Johnson repeated his call for Western countries to send the weapons Ukraine needs.
"The sooner we can help the Ukrainians to their inevitable victory, the sooner their suffering will be over, and the sooner the whole world, including Russia, can begin to recover from Putin's catastrophe," he wrote.
"That requires all of us in the West, all the friends of Ukraine, to double and treble our support."
