U.S. Defense Secretary Lloyd Austin met Germany's new Defense Minister Boris Pistorius on Thursday to press Berlin to allow the transfer of German-made tanks to Ukraine, U.S. officials said, as the two allies remained at loggerheads over the issue.

Germany will allow German-made tanks to be sent to Ukraine to help its defense against Russia if the United States agrees to send its own tanks, a German government source told Reuters.

But U.S. officials publicly and privately insist that Washington has no plans to send U.S-made tanks to Ukraine for now, arguing that they would be too difficult for Kyiv to maintain and would require a huge logistical effort to simply run.

"The secretary will be pressing the Germans on this," one senior U.S. defense official said.

Before the talks started, Austin thanked Germany for its support for Ukraine so far.

"Germany remains one of our most important allies ... I'd like to thank the German government for all that it has done to strengthen Ukraine's self-defense," Austin said, without specifically mentioning the issue of tanks.

Pistorius, speaking just hours after taking office, said Germany was ready to support Kyiv.

"Together with our partners, we will continue to support Ukraine in its struggle for freedom and territorial independence and sovereignty," the German said.

The senior U.S. defense official said supplying Ukraine with German-made Leopard tanks made most sense as a number of countries already had them and were willing to transfer them quickly.

The United States has committed roughly $24 billion to help Ukraine to defend itself against Russian forces.

A second U.S. official said President Joe Biden's administration was set to approve a new aid package to Ukraine, worth more than $2 billion.

The package, which could be announced as early as Friday at a meeting of defense leaders at Ramstein Air Base in Germany, would likely include Stryker armored vehicles for Kyiv, but not M1 Abrams tanks.

The United States aims to break the dynamic of grinding warfare and near-frozen front lines in Ukraine with newly announced military capabilities that it hopes will breathe fresh momentum into Kyiv's battle against Russian forces, a senior Pentagon official said on Wednesday.

But Colin Kahl, the Pentagon's top policy adviser, said the Pentagon still was not prepared to meet Kyiv's calls for gas-guzzling M1 Abrams main battle tanks.

Some Eastern European officials have publicly called on Germany to allow the transfer of Leopard tanks to Ukraine and Polish Prime Minister Mateusz Morawiecki on Monday urged Germany to send Ukraine the weaponry it needed.

Britain has said it would send 14 Challenger 2 tanks, its main battle tanks, and additional artillery support to Ukraine, a step officials hope will open the door for Germany to make similar moves.

Some U.S. officials remain hopeful that they can convince Germany to allow the transfer of third party tanks to Ukraine.

"We are very optimistic that we will make progress on this requirement by the end of the week," a second U.S. official said.