(CNSNews.com) - Defense Secretary Lloyd Austin, speaking at NATO headquarters in Brussels on Wednesday, said "we still have much more to do" for Ukraine's defense, even as the U.S. and its allies "must all replenish our stockpiles to strengthen our deterrence and defense for the long term."

Austin had just concluded a meeting with other NATO defenders of Ukraine's sovereignty.

"At the Madrid summit in June, NATO leaders agreed on a fundamental shift in our collective defense and deterrence," Austin told a news conference:

"We are strengthening our capabilities for the long-term, to deter and defend against all threats, across all domains. We're upgrading our defense plans and putting more forces at higher levels of readiness.

"Today, we discussed the progress that we've made since Madrid and our ongoing work as we move towards the Vilnius summit in July."

Austin said the allies, in Vilnius, "will agree on a new defense investment pledge" -- meaning more money and materiel for Ukraine. "We had productive conversations about that pledge, and we look forward to working with our valued allies to ensure that we all do even more to invest in our shared security," he said.

"We also discussed our progress in building up ammunition stockpiles and boosting defense-industrial capacity. And NATO allies have dug deep over the past year, and both President Biden and I are deeply grateful.

"But we still have much more to do. Even as we rush to support Ukraine in the critical months ahead, we must all replenish our stockpiles to strengthen our collective defense."

Ukraine, meanwhile, is warning of a renewed push by Russian forces as spring approaches.

Austin noted that Russia continues to send large numbers of troops to the fight, but they are poorly trained and equipped. "That’s their strength. They have a lot of people,” Austin said.

“Our goal is to make sure that we give Ukraine additional capability so they can be not only marginally successful, they can be decisive on the battlefield and upcoming offensive.”

Austin emphasized that NATO "will not be drawn into Putin's war of choice."

But he said NATO will "never waver" in defending its people and its territory. "America's commitment to that core mission is unflinching," he said, and "America's commitment to Article 5 is ironclad."

Austin said the outcome of Putin's war, begun nearly one year ago, "is profoundly important to Ukrainian security, European security, and to global security."

According to a January 2023 report from the Congressional Research Service:

"The United States has been a leading provider of security assistance to Ukraine, particularly since Russia launched its renewed and expanded invasion of Ukraine on February 24, 2022.

"From 2014, when Russia first invaded Ukraine, through January 25, 2023, the United States has committed more than $29.9 billion in security assistance 'to help Ukraine preserve its territorial integrity, secure its borders, and improve interoperability with NATO.'

"Of this amount, the Biden Administration has committed more than $27.1 billion in security assistance since the start of the 2022 war. FY2022 and FY2023 security assistance packages aremostly being funded via $48.7 billion in supplemental appropriations.

"This amount includes $25.93 billion to replenish Department of Defense equipment stocks sent to Ukraine via presidential drawdown authority; $18 billion for DOD’s Ukraine Security Assistance Initiative and $4.73 billion in Foreign Military Financing for Ukraine and 'countries impacted by the situation in Ukraine.'

"Supplemental appropriations also include funds for U.S. European Command operations and related support for the U.S. military."

In 2022, the United States has provided more advanced defense equipment to Ukraine, as well as greater amounts of previously provided equipment.