More than 140 heads of state and government are due to take part in the debate at the UN General Assembly getting under way on September 24 at UN headquarters in New York.
The threat posed by Islamic State militants is expected to top the issues raised by leaders, along with the spread of Ebola virus in western Africa, plus Russia's aggressive actions in Ukraine, including its annexation of Crimea.
Debate at the UN General Assembly last to September 30.
U.S. President Barack Obama will be among the first speakers to address the General Assembly on September 24.
The debate starts a day after the United States -- along with five Arab nations -- launched air strikes on IS targets inside Syria, the first such military action in that country.
Obama hailed the support of the Arab nations, saying: "This is not America's fight alone."
IS now controls territory stretching from northern Syria to the outskirts of Baghdad.
The militants have established what they call an Islamic state, or caliphate, ruled by their harsh interpretation of Islamic law.
On the sidelines of the General Assembly debate, Obama will lead a summit meeting of the Security Council on September 24 to focus on one aspect of the threat — foreign terrorist fighters.
A draft resolution expected to be adopted by the 15-member council would require all countries to prevent the recruitment and transport of would-be foreign fighters preparing to join terrorist groups such as the Islamic State.
His country facing scorn and sanctions for its actions in Ukraine, Russian President Vladimir Putin will be among the notable no-shows at the General Assembly.
The Kremlin will instead be represented by Foreign Minister Sergei Lavrov, who will address the General Assembly on September 27.
Based on reporting by AP and Reuters