Mr Poroshenko's office said the two men spoke by telephone yesterday and the Ukrainian President emphasized he was ready to return to a ceasefire as soon as hostages were released and independent observers allowed in to monitor Ukraine's border with Russia.
Kiev called off a unilateral ceasefire on Tuesday after numerous attacks by the separatists on Ukrainian forces. Ukraine accuses Russia of allowing fighters and weapons to enter Ukraine through their common border.
Mr Poroshenko has also won parliamentary approval to shake up the leadership of the armed forces as they struggle to end the rebellion by pro-Russian separatists.
Parliament endorsed Colonel-General Valery Heletey as defence minister after hearing Mr Poroshenko describe the 46-year-old as a man "who will work day and night for restoring the military capability of our armed forces".
Mr Poroshenko took office last month with the country in crisis, as two eastern regions press demands to break away and join Russia, following the example of Crimea earlier this year.
After months of unsuccessful attempts to quash the uprising, he wants to sharpen the army's effectiveness while exploring diplomatic options to end the crisis, which has revived East-West tensions in ways reminiscent of the Cold War.
Kiev says 200 service personnel have been killed since the start of the conflict, as well as hundreds of civilians and rebels.
In Donetsk, the main city of the east, where separatists have controlled key buildings since April, three traffic policemen were shot dead and one was wounded by gunmen in combat fatigues yesterday.
A Ukrainian soldier was also killed when rebels approached in a car bearing a white flag and then opened fire. Nine border guards were also injured in a mortar attack.