The United Nations has adopted a resolution supporting efforts by Russia and Turkey to end violence in Syria and start peace negotiations.
Russia and Turkey announced the ceasefire this week, the third truce this year seeking to end the nearly six years of war in Syria.
Peace talks between President Bashar al-Assad's government and rebel forces in Syria are set to take place next year in Kazakhstan.
Gunfire has been reported shortly after a ceasefire deal took effect at midnight (10pm GMT), Syrian activists have said.
The London-based Syrian Observatory for Human Rights said shooting was heard in the southern Syrian provinces of Deraa and Quneitra.
The Observatory said there were no reports of casualties, adding that in other areas of Syria warring sides appeared to have ceased firing.
The Democratic presidential candidate may also have shown his cards on his choice of running mate.
The US president also shared a post on Twitter accusing Dr Anthony Fauci of misleading the public over hydroxychloroquine.
Fears over an impending second wave of coronavirus dominates Wednesday’s front pages.