Hours before a partial ceasefire is to be implemented in Syria, US President Barack Obama has warned Russia and Damascus that the "world will be watching." There are looming doubts that the truce will succeed.
Speaking in Washington on Thursday, Barack Obama said the "cessation of hostilities" set to take effect at midnight on Friday "is a potential step in bringing about an end to the chaos" in Syria.
Under the new ceasefire agreement, international powers would be allowed to continue their operations against the "Islamic State" (IS), as well as the al Qaeda-affiliated Nusra Front and similar organizations.
Obama admitted, however, that "even under the best of circumstances we do not expect the violence to end immediately."
"In fact, I think we are certain that there will continue to be fighting," the president said, making particular reference to IS militants.
US officials also expect Russian and Syrian forces to breach the truce. "There's pessimism, not expectation - pessimism," a senior US official told AFP news agency.
Obama's comments on Thursday came hours after UN's Syria envoy, Staffan de Mistura said that Friday was going to be a "crucial day."
Seventeen nations backing Syria's peace process were due to meet in the Swiss city of Geneva on Friday to negotiate further details in the ceasefire. De Mistura is also set to announce a date for a new round of talks between Syria's warring parties.
Syrian President Bashar al-Assad has said his forces and their Russian ally's would have to continue their strikes against the jihadists, but the truce would be off if foreign countries supplied rebels with arms or if anti-government fighters used the truce to rearm themselves. Opposition leaders initially set the period of the ceasefire for two weeks.
Doubts over success
The complex nature of the Syrian war and the differing interests of the participants have cast serious doubt on the ceasefire's success. Syria's Kurdish militia, YPG, told the Reuters news agency on Wednesday that it would halt its fire - but would respond if attacked.
Turkey, which considers YPG an offshoot of the outlawed Kurdish Workers' Party (PKK), has said it will consider the truce broken if it were threatened by the so-called "Islamic State" or the YPG.
If successfully implemented, the ceasefire could see the end of Syria's five-year civil war that has killed more than 260,000 people and forced millions to flee.
ksb/rc (AFP, Reuters)