The United States Defense Secretary, Lloyd Austin, arrived in Berlin on Monday for talks with German officials. 

The main topic of discussion is expected to be Germany's delay in delivering tanks to the U.S. military.

The tanks in question are the Leopard 2A7+ model, which the U.S. had planned to purchase from Germany in order to modernize its own armored vehicle fleet. 

However, Germany has yet to deliver the tanks, citing production delays and other logistical issues.

This has caused frustration on the U.S. side, as the tanks were seen as a crucial component of the country's military modernization efforts. 

The U.S. has also been pressuring Germany to increase its military spending, which has been a point of tension between the two countries in recent years.

During his visit, Secretary Austin is expected to meet with German Defense Minister, Annegret Kramp-Karrenbauer, and other top officials to discuss the tank delivery issue as well as other matters related to defense cooperation between the two countries.

The U.S. has emphasized the importance of strong transatlantic security ties, particularly in light of the ongoing tensions with Russia and the rise of China as a global power. 

As such, the U.S. has been pushing for its NATO allies, including Germany, to increase their military spending and capabilities.

However, Germany has been reluctant to do so, citing domestic budget constraints and other priorities. 

The delay in tank deliveries has added to the already strained relations between the two countries on this issue.

It remains to be seen whether Secretary Austin's visit will result in any concrete agreements or solutions to the tank delivery issue.