It comes after a wave of missiles hit Ukrainian cities on Monday.
The UK and France have pledged to help improve Ukraine's defences after Russia hit the country with a wave of missile strikes on Monday.
London promised to send air defence missiles, while Paris said it would deliver its own anti-aircraft defence systems.
It comes as NATO defence ministers meet for a second day in Brussels on Thursday.
“Russia’s latest indiscriminate strikes on civilian areas in Ukraine warrant further support to those seeking to defend their nation," said Ben Wallace, the UK's Secretary of State for Defence. "So today, I have authorised the supply of AMRAAM anti-aircraft missiles to Ukraine.
“These weapons will help Ukraine defend its skies from attacks and strengthen their overall missile defence alongside the US NASAMS.”
The Pentagon has said it will deliver the first two advanced NASAMS surface-to-air missile systems to Ukraine in the coming weeks, providing Kyiv with a weapon that it has pressed for since earlier this year.
The systems will provide medium- to long-range defences against Russian missile attacks.
Meanwhile, Canada is to provide more than C$47 million (approx. €35m) in new military aid to assist Ukraine in dealing with Russia's invasion, with the package including artillery rounds, satellite communications, winter clothing and drone cameras.
Germany, meanwhile, has recently sent an IRIS-T air defence system to Ukraine and German defence minister Christine Lambrecht said three more would follow next year.
'More air defence top priority' after latest Russian strikes
“Allies have provided air defence, but we need even more. We need different types of air defence, short-range, long-range air defence systems to take out ballistic missiles, cruise missiles, drones, different systems for different tasks,” NATO Secretary-General Jens Stoltenberg said as he arrived at the military alliance's headquarters on Wednesday.
“Ukraine is a big country, with many cities. So we need to scale up to be able to help Ukraine defend even more cities and more territory against horrific Russian attacks.”
Russia targeted critical Ukraine's civilian infrastructure with a deadly wave of missile attacks, including in central Kyiv, on Monday, in retaliation for an explosion that damaged a bridge linking Russia to the illegally annexed peninsula of Crimea.
The missile attacks have been widely condemned by Western allies as war crimes.
Ukrainian forces are believed to have successfully knocked down a significant amount of the missiles that came their way, but the attacks have seen them reiterate calls for more air defence assistance from allies.
At the meeting of the Ukraine Defense Contact Group in Brussels, which has grown to more than 50 members, US Defense Secretary Lloyd Austin said Russia's latest attacks had laid bare its "malice and cruelty" since invading Ukraine.
Ukraine had shifted momentum since September with extraordinary gains but would need more help, he said.
"These victories belong to Ukraine's brave soldiers. But the Contact Group's security assistance, training, and sustainment efforts have been vital," Austin said.
Lethal weapons, artillery, armoured vehicles, and other anti-tank weapons are also on Ukraine's wish list, in particular mounted rocket launchers such as the 18 CAESAR self-propelled howitzers it has received from France or the HIMARS from the US, which have been key to its recapture of territories from Russia.
Kyiv is also calling for allies to provide fuel, communication systems and winter equipment, including clothing.
Oleksii Reznikov, Ukraine's defence minister, who is participating in the meeting of the Contact Group, said he is "feeling optimistic."
Ministers to discuss protecting key infrastructure, strengthening European presence
Also on the agenda will be the alliance's own stocks.
"NATO recently held a meeting of armaments directors to come together and talk about ways that they could jointly address those declining stockpiles and ensure that production can be ramped up to meet the requirements not only of the Ukrainian forces that are fighting so courageously on the ground but also of specific NATO allies," US ambassador to NATO Julianne Smith told Euronews on Tuesday evening.
"So this will be a focus of our work this fall well into the winter to see what we can do to close those gaps," she added.
Standardisation and interoperability — meaning ensuring the various kind of new equipment from the different allies can work together — will be a key focus for ministers.
They will also discuss protecting critical infrastructure after the sabotage of the Nord Stream pipelines late last month as well as the suspected sabotage of a German radio network last week.
"We have doubled our presence in the Baltic and North Seas to over 30 ships" that are "supported by maritime patrol aircraft and undersea capabilities," Stoltenberg has said.
But as private operators own most infrastructure, ministers will need to start thinking about how best to assist them, boost surveillance and make better use of deterrence capabilities.
Nuclear deterrence will also be high on the agenda as NATO allies prepare to take part in their annual "Steadfast Noon" exercise next week despite the repeated nuclear threats from Russian President Vladimir Putin.
"Nuclear deterrence is a key feature of NATO's defence and deterrence posture. As such, the allies do conduct these types of exercises on a regular basis. And so this is not out of cycle. It is not in response to what's happening in Ukraine. This is something that NATO's would be doing irrespective of what's happening on the ground inside Ukraine," Smith said.
"What we know is that there's a lot of loose talk right now about the use of Russia's nuclear arsenal. We obviously find this kind of talk deeply disturbing and dangerous," she said, adding that they had informed the Russians "quite directly that any use of nuclear weapons would be faced with unprecedented consequences."
The drills, which involve training flights with dual-capable fighter jets, as well as conventional jets, backed by surveillance and refuelling aircraft, are intended to ensure that NATO’s nuclear deterrent remains safe, secure and effective.
France, the UK and the US are the only NATO members to have nuclear weapons and some 100 US nuclear warheads are estimated to be stored across Europe and thought to be in Belgium, Germany, Italy, the Netherlands and Turkey.
France also announced on Tuesday that it was upping its deterrence contribution on the alliance's eastern flank.
The country will add 200 troops to the 500 it has already deployed to Romania, where it leads a multinational battlegroup as well as armoured fighting vehicles, including tanks.
Rafale fighter jets will be deployed to Lithuania to patrol, while a light infantry company is to be dispatched to Estonia.
Romania President Klaus Iohannis described the announcement as "an important gesture for NATO's Eastern flank, a sign of solidarity between the Allies", while his Lithuanian counterpart, Gitanas Nausėda, said it represents "a strong signal of unity & solidarity against Russian aggression in Ukraine."