RAMSTEIN AIR BASE, Germany (AP) — Ukrainian President Volodymyr Zelenskyy and U.S. Defense Secretary Lloyd Austin used their final meeting Thursday to press the incoming Trump administration not to give up on Kyiv’s fight, with Austin warning that to cease military support now “will only invite more aggression, chaos and war.”

“We’ve come such a long way that it would honestly be crazy to drop the ball now and not keep building on the defense coalitions we’ve created,” Zelenskyy said. “No matter what’s going on in the world, everyone wants to feel sure that their country will not just be erased off the map.”

President-elect Donald Trump’s pronouncements about pushing for a quick end to the war, his kinship with Russian President Vladimir Putin and uncertainty over whether he will support further military aid to Ukraine have triggered concern among allies.

The Biden administration has worked to provide Ukraine with as much military support as it can, including approving a new $500 million package of weapons and relaxing restrictions on missile strikes into Russia, with the aim of putting Ukraine in the strongest position possible for any future negotiations to end the war.

Austin doubled down on Zelenskyy’s appeal, saying “no responsible leader will let Putin have his way.”

And while Austin acknowledged he has no idea what Trump will do, he said the international leaders gathered Thursday at Ramstein Air Base talked about the need to continue the mission.

The leaders were attending a gathering of the Ukraine Defense Contact Group, a consortium of about 50 partner nations that Austin brought together months after Russia invaded Ukraine in February 2022 to coordinate weapons support.

“I’m leaving this contact group not with a farewell but with a challenge. The coalition to support Ukraine must not flinch. It must not falter. And it must not fail,” Austin said during his final press conference. “Ukraine’s survival is on the line. But so is all of our security.”

Some discussed what they would do if the U.S. backed away from its support for Kyiv, if the contact group would assume a new shape under one of its major European contributors, such as Germany. Germany’s Defense Minister Boris Pistorius said his country and several other European nations are discussing options.

Austin said the continuation of the group is essential, calling it “the arsenal of Ukrainian democracy” and “the most consequential global coalition in more than 30 years.”

President Joe Biden was to have his final face-to-face meeting with Zelenskyy in the coming days in Rome, but he canceled the trip because of the devastating fires in California.

Pistorius said he intends to travel to the U.S. shortly after Trump’s Jan. 20 inauguration to meet his new counterpart to discuss the issue.

“It’s clear a new chapter starts for Europe and the entire world just 11 days from now,” and it will require even more cooperation, Zelenskyy said.

Ukraine has launched a second offensive in Russia’s Kursk region and is facing a barrage of long-range missiles and ongoing advances from Russia as both sides seek to put themselves in the strongest negotiating position possible before Trump takes office.

Zelenskyy called the Kursk offensive “one of our biggest wins,” which has cost Russia and North Korea, which sent soldiers to help Russia, thousands of troops. Zelenskyy said the offensive resulted in North Korea suffering 4,000 casualties, but U.S. estimates put the number lower at about 1,200.

Zelenskyy said Ukraine will continue to need air defense systems and munitions to defend against Russia’s missile attacks.

The latest U.S. aid package includes missiles for air defense and for fighter jets, sustainment equipment for F-16s, armored bridging systems and small arms and ammunition.

The weapons are funded through presidential drawdown authority, meaning they can be pulled directly from U.S. stockpiles, and the Pentagon is pushing to get them into Ukraine before the end of the month.

Unless there is another aid package approved, the Biden administration will leave about $3.85 billion in congressionally authorized funding for any future arms shipments to Ukraine. It will be up to Trump to decide whether or not to spend it.

“If Putin swallows Ukraine, his appetite will only grow,” Austin told the contact group leaders. “If tyrants learn that aggression pays, we will only invite even more aggression, chaos, and war.”

In the months since Trump’s election victory, Europeans have grappled with what that change will mean in terms of their fight to keep Russia from further advancing, and whether the post-World War II Western alliance will hold.

In recent days, Trump has threatened to take Greenland, which is part of the Kingdom of Denmark — a NATO member — by military means if necessary. Such action would upend all norms of the historic NATO alliance and possibly require members to come to the defense of Denmark.

Austin declined to comment on Trump’s threat, but Pistorius called it “diplomatically astonishing.”

“Alliances are alliances, to stay alliances. Regardless of who is governing countries,” Pistorius said. “I’m quite optimistic that remarks like that won’t really influence U.S. politics after the 20th of January.”

Globally, countries including the U.S. have ramped up weapons production as the Ukraine war exposed that all of those stockpiles were woefully unprepared for a major conventional land war.

The U.S. has provided about $66 billion of the total aid since February 2022 and has been able to deliver most of that total — between 80% and 90% — already to Ukraine.