Putin spoke a day after Assad made a surprise visit to Moscow for talks with the Russian leader.
The Free Syrian Army rebel group confirmed the death of its chief of staff, Basil Zamo, formerly a captain in the Syrian military.
The government in Havana called the allegations "irresponsible and unfounded."
Obama said the Syrian civil war could only end with a political solution leading to a new inclusive government.
Government troops and their allies backed by Russian jets have launched an offensive against rebels near Aleppo.
The offensive builds on over a week of ground attacks launched with Russian air support.
Amnesty International said the YPG have forcibly displaced thousands of villagers in northeastern Syria.
The move came weeks after Moscow raised the stakes with its intervention in the long-running civil war.
Republican senators condemned the program as a "total failure."
Nobody in Washington appears to care about the latest instance of U.S. mission creep in Syria's civil war.
18-year-old Thomas van Linge's maps show the changing faces of Iraq and Syria.
Mouhannad Droubi was arrested over a "torture-like" assault in Syria that was recorded.
Some fighters, like Ahmed al-Hussein, care for entire packs of dogs.
The U.S. military plans to train troops to beat back the Islamic State in Syria.
France is to decide whether it will aid Jordan in its fight against ISIS by sending fighter jets to the country
Sherko Omer left his native Iraq hoping to join the fight against Assad in Syria, but soon found himself caught up in a horrifying sectarian war, unable to escape