WASHINGTON (AP) — 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 were meeting Monday to coordinate more military aid to Ukraine, as Kyiv tries to hold off a Russian offensive in the northeast while launching its own massive assault on the Russia-occupied Crimean Peninsula.

“We’re meeting in a moment of challenge,” Austin said, noting that Russia’s new onslaught of Kharkiv showed why the continued commitment by the countries was vital to keep coming. Austin vowed to keep U.S. weapons moving “week after week.”

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.