Trump is speaking amid worsening tensions between the U.S. and Iran.
While the U.S. president has not ruled out meeting with Iranian President Hassan Rowhani, who will address the assembly on Wednesday, the chance of that happening seems unlikely.
Tensions have been rising between the two nations ever since Trump pulled Washington out of a 2015 deal between Tehran and world powers, in spite of no sign then of violations by Iran.
The agreement aimed at preventing Tehran from obtaining a nuclear weapon.
Trump has since been imposing tough sanctions on Iran, seeking to cripple the country’s economy and force the country to change its foreign policy.
There have been concerns in recent months that the countries could go to war, most recently after an attack on a Saudi Arabian oil field, which is largely being blamed on Tehran.
Iran rejects responsibility. Trump says he is showing restraint, for now, and is not launching strikes.
Also addressing the UN on Tuesday will be Brazilian President Jair Bolsonaro, Turkish President Recep Tayyip Erdogan, French President Emmanuel Macron, Egyptian President Abdel Fattah al-Sissi and British Prime Minister Boris Johnson, among others.
The General Debate session comes a day after the UN held a major summit on climate change.
Trump will hold a series of bilateral meetings during the day, including with U.K. Prime Minister Boris Johnson, Indian Prime Minister Narendra Modi, UN Secretary General Antonio Guterres and Iraqi President Barham Salih.