Defense Secretary Lloyd Austin committed Monday to keeping U.S. weapons moving to Ukraine as Kyiv faces one of its toughest moments against a renewed assault by Russia.

Austin and as many as 50 defense leaders from Europe and around the world met Monday to coordinate more military aid to Ukraine as it tries to hold off a Russian offensive in the northeast while launching its own massive assault on the Russia-occupied Crimean Peninsula.

鈥淲e鈥檙e meeting in a moment of challenge,鈥� Austin said, noting that Russia鈥檚 new onslaught on Kharkiv, Ukraine鈥檚 second-largest city, showed why the commitment was vital. Austin vowed to keep U.S. weapons moving 鈥渨eek after week.鈥�

Austin told reporters the group spent a lot of time talking about Ukraine鈥檚 critical need for air defense systems, which he said are helping stave off the Russian attacks.

鈥淲e鈥檒l continue to push to ensure that Ukraine owns its skies and can defend its citizens and its civilian infrastructure far from the front lines,鈥� he said after the meeting ended.

Speaking alongside Austin, Gen. CQ Brown, chairman of the Joint Chiefs of Staff, said that while there are no plans now to put U.S. trainers back into Ukraine to work with Ukrainian forces, the U.S. could do that after the war.

鈥淥nce this conflict is over and we鈥檙e in a better place, then I would suspect we would be able to bring trainers back in,鈥� he said.

The U.S. announced no new aid packages Monday, even as Ukrainian forces continue to complain that weapons are just trickling into the country after being stalled for months due to congressional gridlock over funding. Pentagon officials have said that weapons pre-positioned in Europe began moving into Ukraine soon after the aid funding was approved in late April.

It鈥檚 unclear how much of that has reached some of the front lines, where Russian troops have intensified their assault.

Russian President Vladimir Putin said on Friday during a visit to China that Moscow鈥檚 offensive in the northeastern Kharkiv region aims to create a buffer zone but there are no plans to capture the city.

Ukrainian troops have been fighting to halt Russian advances in the Kharkiv region, while also increasing their offensive attacks in Crimea, including on military infrastructure on the Black Sea coast and in the Russian-occupied city of Sevastopol.

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Ukraine has struggled to get enough troops to the front lines, as the war drags on into its third year and fighting takes its toll. In an effort to increase troop numbers, President Volodymyr Zelenskyy signed two laws, allowing prisoners to join the army and increasing fines for draft dodgers fivefold. The controversial mobilization law goes into effect on Saturday.

In the four weeks since President Joe Biden signed the $95 billion foreign aid package, which included about $61 billion for Ukraine, the U.S. has sent $1.4 billion in weapons pulled from Pentagon stockpiles and announced it was providing $6 billion in funding through the Ukraine Security Assistance Initiative. USAI pays for longer-term contracts with the defense industry and means that the weapons could take many months or years to arrive.

In recent packages the U.S. has agreed to send High Mobility Artillery Rocket Systems (HIMARS) and rockets for them, as well as munitions for Patriot and National Advanced Surface-to-Air Missile Systems, artillery, anti-aircraft and anti-tank munitions, and an array of armored vehicles, such as Bradley and Mine Resistant Ambush Protected vehicles.

The U.S. is also providing additional coastal and riverine patrol boats, trailers, demolition munitions, high-speed anti-radiation missiles, protective gear, spare parts and other weapons and equipment.

The State Department has also approved a proposed emergency sale of HIMARS to Ukraine for an estimated $30 million. State said Ukraine has asked to buy three of the rocket systems, which would be funded by the government of Germany.

The U.S. has now provided about $50.6 billion in military assistance to Ukraine since Russia invaded in February 2022.

Lolita C. Baldor And Tara Copp, The Associated Press