The Ukrainian military said late today that no soldiers had been killed in the past 24 hours for the first time since fighting over the blue-collar town of Avdiivka soared last Sunday.
A total of 27 people have died in the battered town, while eight more have been killed in other parts of the war zone that covers the separatist fiefdoms of Lugansk and Donetsk in Ukraine's eastern rustbelt.
Ukrainian military spokesman Sergiy Klymenko told AFP in Avdiivka that a pause in hostilities agreed by the two sides came into effect at 8:00 am (0600 GMT).
But he stressed that it was only a verbal deal and not a written commitment.
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"We are still a long way off a complete ceasefire," added Oleksandr Motuzyanyk, a Ukraine military spokesman in Kiev.
Klymenko said the truce was aimed at allowing workers to repair broken power lines after many in the town of 25,000 -- nearly 300 of whom have been evacuated -- spent days without power or heat and only limited supplies of water.
Nearly all the town's residents work in a giant coke plant that supplies much of the electricity in Ukraine's east.
Poroshenko's first conversation with the new US leader since his inauguration took place as the impoverished former Soviet Republic worries that Trump is seeking to build a friendship with Russian counterpart Vladimir Putin.
Some analysts say they believe this potential improvement in relations with Moscow had emboldened the rebels and was behind the upsurge in fighting in Avdiivka.
Others attributed it to a battle for power within the insurgent movement and the right for its warlords to brag about who staged the biggest attack.
"We will work with Ukraine, Russia, and all other parties involved to help them restore peace along the border," the White House quoted Trump as saying.
Washington also said the two leaders had a "good call" but provided few other details except to note that a meeting between Trump and Poroshenko was in the works.