Under tight security, Ukrainian President Volodymyr Zelenskyy on Sunday visited a Pennsylvania ammunition factory to thank the workers who are producing one of the most critically needed munitions for his country's fight to fend off Russian ground forces.

The Ukrainian president is expected to visit the Scranton Army Ammunition Plant before addressing the U.N. General Assembly this week in New York.

Two of the Pentagon leaders who have pushed that increased production through -- Doug Bush, assistant secretary of the Army for acquisition, logistics and technology and Bill LaPlante, the Pentagon's top weapons buyer -- are also expected to join Zelenskyy at the plant, as is Democratic Pennsylvania Gov. Josh Shapiro.