Russian trucks loaded with humanitarian supplies had been idling at the border, but some have now entered Ukraine without permission, which Kiev considers an act of aggression. Russian and Ukrainian leaders are to meet next week.
Islamic State militants had demanded millions of dollars for James Foley's release. While the US government refuses to pay ransoms to kidnappers, some European governments have done so in the past, enriching Al Qaeda and its affiliates.
The new truce is to last through Monday. Talks in Cairo on ending the conflict in Gaza mark the first time Israel and Hamas have negotiated, albeit indirectly, on something other than prisoner exchanges.
The US is developing a plan to rescue members of the Yazidi minority group amid increasing calls from the Kurdish government and Yazidi leaders for the US to respond more forcefully against Islamic State militants.
Territorial gains by Kurdish fighters and relief for stranded Yazidis follow the first days of US military intervention in Iraq. Britain and France are also getting involved. But the Islamic State remains a potent threat.
At a UN Security Council meeting, Russia raised concerns over displacement in eastern Ukraine and called for greater aid to civilians. Critics say Russia is cloaking its true intentions in a conflict that it helped seed.