U.S. President Barack Obama speaks at the 69th United Nations General Assembly at United Nations Headquarters on Sept. 24, 2014, in New York City. Andrew Burton/Getty Images

President Barack Obama defended U.S. airstrikes in Syria Wednesday before the U.N. General Assembly, stating that they are necessary to destroy the Islamic State group's "network of death." Obama's speech comes days after the White House authorized the beginning of a U.S. bombing campaign over the Middle Eastern country, a military maneuver that Russia and Iran have deemed illegal.

"We come together at a crossroads between war and peace, between disorder and integration, between fear and hope," Obama said. Syria is "the heart of darkness," and "the only language these terrorist groups understand is force," Obama said, adding: "Today I ask the world to join this effort."

The U.S. military began the airstrikes targeting Islamic State and other militant groups within Syria late Monday. Five Arab states are supporting the U.S., while France is striking against the Islamic State group in Iraq at the request of the Iraqi government. Obama launched similar strikes against the militant group also known as ISIS and ISIL in August.

During his speech, Obama lauded Muslim leaders worldwide working to counter the extreme form of Islam that the Islamic State group advocates. "Here I'd like to speak directly to young people across the Muslim world," he said. "You come from a great tradition that stands for education, not ignorance; innovation, not destruction; the dignity of life, not murder. Those who call you away from this path are betraying this tradition, not defending it."

Obama also addressed this summer's bloody conflict between Israel and Hamas, saying that the "status quo in the West Bank and Gaza is not sustainable."

"So long as I am president, we will stand up for the principle that Israelis, Palestinians, the region and the world will be more just with two states living side by side, in peace and security,” he said.

Obama urged the U.N. to embrace the 21st century, calling the world's issues "symptoms of a broader problem: the failure of our international system to keep pace with the modern world," and saying "we cannot rely on a rule book written for a different century."

He also called on his counterparts in other nations to help combat the growing Ebola outbreak in West Africa and to stop Western militants from traveling freely from the Middle East and Europe and North America.

His speech ended with an acknowledgment that the U.S. has "plenty of problems within our own borders," a nod to the recent racially driven riots in Ferguson, Missouri, after a police officer killed an unarmed teenager.

Apart from his speech, Obama is expected to be busy on the sidelines during this week's U.N. gathering, building support for the U.S.-led actions in Syria. He was scheduled Wednesday to meet one-on-one with Iraqi Prime Minister Haider al-Abadi and U.S. Secretary General Ban Ki-moon. He also will attend a Security Council summit on foreign terrorist fighters after addressing the General Assembly.

Obama's busy schedule Wednesday came a day after he spoke at the U.N.'s climate summit, when he passionately rallied other nations to fight climate change alongside the U.S. He said that the U.S. and China have a "special responsibility" to lead the fight.

"There should be no question that the United States of America is stepping up to the plate," Obama said. "We recognize our role in creating this problem. We embrace our responsibility to combat it. We will do our part and we will help developing nations to do theirs."

Obama was the second world leader to speak at Wednesday's general assembly, after Brazilian President Dilma Rousseff. The general debate gives all U.N. member states approximately 15 minutes to outline their priorities to the other 192 world leaders gathered in the U.N. Assembly Hall. Other notable delegation speeches scheduled for Wednesday included the Republic of Korea, France, Turkey, Nigeria and the United Kingdom.

Syria's government is expected to address the General Assembly Monday morning. Watch a live stream of the General Assembly addresses here.