DIRMISKES, Lithuania (AP) — Polish President Andrzej Duda said Friday that “a potential aggressor must see our readiness” as he and his Lithuanian counterpart monitored a joint military drill along their shared border.

Duda and Lithuanian President Gitanas Nausėda met on the last day of the week-long Brave Griffin 24/II military exercise along the Suwalki Gap, a strategically important stretch of land that’s considered a potential flashpoint area in case of a standoff between Russia and NATO.

The border, almost 100 kilometers (62 miles) long between NATO members Poland and Lithuania, is also a land corridor between Belarus, a Moscow ally, and Russia’s Baltic Sea exclave of Kaliningrad.

“There is a potential threat, which is why these exercises are going on,” Duda said.

The drill included 1,500 Lithuanian infantry soldiers, nearly 200 members of Poland’s 15th Mechanized Brigade, and U.S. and Portuguese military personnel.