Both leaders will speak in the afternoon session, which begins at 3 p.m. EDT. The morning session begins at 9 a.m.
Zelensky was at the center of the impeachment of U.S. President Donald Trump last year, which grew out of phone calls between the leaders in which they discussed investigating Democratic presidential nominee Joe Biden and his son Hunter, a former Ukrainian gas company executive.
The articles of impeachment said Trump abused his power and obstructed a congressional investigation. He was impeached by the Democratic-controlled House last December and acquitted in the Republican-held Senate in February.
Ghani's U.S.-backed Afghanistan government is currently in peace talks with the Taliban, which could lead to the total withdrawal of U.S. forces.
Lebanon has been facing a severe economic crisis for years and is grappling with a series of fires and explosions that have occurred over the past month, including one in early August in the Port of Beirut that killed almost 200 people.
This year's General Assembly is mostly virtual due to COVID-19. Secretary-general Antonio Guterres opened the high-level debate on Tuesday at U.N. headquarters in New York City, but all of the addresses, including that of U.S. President Donald Trump and a speech by South Korean President Moon Jae-in, were made remotely.
Only one mask-wearing diplomat from each of the nations that make up the United Nations is permitted to sit in the General Assembly Hall during this year's debate.