Updated 9:41 a.m.: Putin calls for anti-terror coalition
President Vladimir Putin has urged the creation of a broad anti-terror coalition that would include the Syrian government troops.
Addressing the U.N. General Assembly, Putin said it was a "huge mistake" not to engage the Syrian army in the fight against the Islamic State group.
He also criticized the West for arming "moderate" rebels in Syria, saying they later come to join the Islamic State terror group.
Without naming the United States, he said a "single center of dominance has emerged after the end of Cold War," and attempts have been made to revise the U.N. role.
Updated 8:07 a.m.: US willing to work with Russia, Iran on Syria crisis, Obama says
Straining for a solution to Syria's civil war, President Barack Obama on Monday said the United States is willing to work with Russia, as well as Iran to achieve a "managed transition" to remove Syrian leader Bashar Assad from power.
Syria cannot "return to the pre-war status quo," Obama declared during his annual address to the United Nations General Assembly.
The president's remarks underscore the tensions between the U.S. and Russia, Assad's strongest ally. Assad's future was expected to be a top issue during a rare face-to-face meeting late Monday between Obama and Russian President Vladimir Putin.
Putin was to address the U.N. General Assembly after Obama. He was expected to argue that Assad's military is the most capable force for fighting the Islamic State — the extremist group with key strongholds in Syria and Iraq — and therefore needs to be strengthened.
Obama rejected Putin's continued support for Assad, saying that simply arguing that the "alternative is surely worse" is not a solution to a crisis that has killed more than 250,000 people since it began in 2011, led to a flood of refugees and created a vacuum for the Islamic State and other extremist groups.
Despite Obama's staunch opposition to Assad remaining in power, the U.S. has struggled to energize a political process to push him from power. Russia has long been a major obstacle, shielding Assad from U.N. sanctions and continuing to provide the Syrian government with weapons.
In fact, Russia has appeared to deepen its support for Assad in recent weeks, sending additional military equipment and troops with the justification that it is helping the government fight the Islamic State.
"There is no other solution to the Syrian crisis than strengthening the effective government structures and rendering them help in fighting terrorism," Putin said in an interview with CBS' "60 Minutes" that aired on the eve of his meeting with Obama.
Putin's calls for strengthening Assad's military come amid notable troubles for Obama's plan to train and arm moderate rebels to fight the Islamic State in Syria. A $500 million Pentagon training program has resulted in just a handful of fighters to bolster airstrikes from a U.S.-led coalition.
The U.S. has agreed to talk with Russia about its military action in Syria. U.S. Defense Secretary Ash Carter spoke to his Russian counterpart about Syria earlier this month, the first military-to-military conversation in more than a year.
Addressing another area of tension with Russia, the U.S. president defended Western sanctions against Moscow for its actions supporting rebels in Ukraine. Obama said he wasn't seeking a return to the Cold War, but argued that the United States couldn't stand by while a nation's sovereignty was being violated.
"If that happens without consequences in Ukraine, it could happen to any nation gathered here today," Obama said.
The Ukraine crisis has indeed driven U.S.-Russian relations to post-Cold War lows. Russia annexed Crimea from Ukraine in 2014 and a pro-Russian armed insurgency continues in eastern Ukraine, with Kiev and NATO accusing Moscow of backing and supplying it.
A shaky peace deal for Ukraine was brokered in February by France and Germany, and Russia doesn't want the United States to become engaged in those talks. Another four-way meeting of leaders of Russia, Ukraine, France and Germany is set to take place in Paris this weekend.
U.S. officials say Obama will stress to Putin the importance of local elections in Ukraine going forward in October without interference.
— Associated Press reporters Julie Pace and Vladimir Isachenkov
6:58 a.m.: Obama, Putin likely to address Syria
President Barack Obama and Russian President Vladimir Putin will meet in New York Monday, but first they will each get a chance to present their case to the rest of the world by addressing the United Nations General Assembly. And their disagreement over Syria may be at the forefront.
Obama is looking for a political resolution to Syria's civil war that includes the ouster of President Bashar Assad, a Russian ally. Putin, meanwhile, is expected to argue that Assad's military is the most capable force for fighting the Islamic State.
You can watch Obama's speech in the video above starting at about 7 a.m. PT.
Meanwhile, U.N. Secretary-General Ban Ki-Moon for the first time is calling for the situation in Syria to be referred to the International Criminal Court.
In his state of the world address to leaders from the U.N.'s 193 member states, Ban says "innocent Syrians pay the price of more barrel bombs and terrorism" and there must be no impunity for "atrocious" crimes.
His call opened the annual General Assembly gathering of world leaders that includes addresses from Obama, Putin and Chinese President Xi Jinping on Monday morning alone.
Ban says five countries "hold the key" to a political solution to Syria: Russia, the U.S., Saudi Arabia, Turkey and Iran.
The U.N. chief says the Syrian conflict is "driven by regional powers and rivalries."
FAQ: A look at the UN General Assembly
The annual U.N. General Assembly ministerial meeting is always a major event, but this year's is extraordinary. It could bring a record number of world leaders, including Russian President Vladimir Putin, who hasn't attended in years. Most of the attention will be on Putin and President Barack Obama who will have their own separate meeting in New York at a time of tensions over Russia's military involvement in Syria.
Here's a look at this year's U.N. General Assembly:
WHAT IS THE GENERAL ASSEMBLY?
The General Assembly is the global body that represents all 193 U.N. member states. It meets throughout the year and is the forum where any global issue can be discussed, including those related to international peace and security. While it can make recommendations, its resolutions are not binding. It does have power over the U.N. budget, which it must approve, and it can and has adopted many global treaties. It holds an annual ministerial meeting in September called the General Debate that brings world leaders to U.N. headquarters. It begins Monday morning.
WHO IS ATTENDING?
According to U.N. officials about 160 world leaders are expected to attend this year's ministerial meeting. Among the big names expected besides Obama and Putin are China's President Xi Jinping, Iran's President Hassan Rouhani, German Chancellor Angela Merkel and French President Francois Hollande.
HOW IS THIS DIFFERENT FROM PAST GENERAL ASSEMBLY MEETINGS?
This is the 70th anniversary of the United Nations and it is bringing an unusually large number of presidents, prime ministers, kings and rulers to U.N. headquarters in New York. The high turnout is also a result of the three-day U.N. summit that ended Sunday, which was called by Secretary-General Ban Ki-moon to adopt new U.N. development goals for the next 15 years to eradicate poverty and preserve the planet. There are 17 goals and 169 targets.
DIDN'T MOST OF THESE LEADERS ALREADY ADDRESS THE UNITED NATIONS?
Many leaders came early to address the development summit. Some are addressing only the summit and some are addressing only the ministerial session. The summit speeches focused on new U.N. development goals and how to achieve them. The speeches at the annual gathering of presidents, prime ministers, and crowned leaders which starts Monday and ends Saturday are more wide-ranging, touching on global crises and conflicts as well as major social and economic issues.
WHAT ARE THE BIG ISSUES THIS YEAR?
World leaders are grappling with how to end the Syrian conflict that is now in its fifth year and has killed over 250,000 people, how to counter the spread of extremism in the Middle East and Africa and how to deal with the upsurge in migrants fleeing from Syria and other conflicts including in Iraq, Yemen and Afghanistan.
WHAT SHOULD WE LOOK FOR?
Hundreds of bilateral meetings are taking place from glitzy hotel suites to U.N.-created cubicles. The most highly anticipated and closely watched will be Monday night's meeting between Obama and Putin, their first face-to-face encounter in nearly a year. Obama is chairing a major meeting Tuesday to tackle growing extremism. Russian Foreign Minister Sergey Lavrov, whose country holds the presidency of the U.N. Security Council this month, is chairing a ministerial meeting of the council Wednesday on counter-terrorism.
— Edith M. Lederer/Associated Press
This story has been updated.