KIEV (AFP) ― Ukraine President Petro Poroshenko gets down to work Sunday, after vowing at his inauguration to avert civil war and mend ties with Russia as his nation faces disintegration and economic collapse.

Poroshenko took the oath of office on Saturday, the day after holding his first meeting with Russian President Vladimir Putin since a May 25 election victory entrusted him with stemming a bloody crisis that has shaken the post-Cold War order and redrawn Europe’s map.

The 48-year-old candy magnate ― dubbed the “chocolate king” ― first asked a packed session of parliament to observe a minute of silence for the 100 people killed in three days of a brutal crackdown in Kiev that led to the February ouster of Ukraine’s Kremlin-backed regime.

The self-made billionaire then vowed to grant amnesty to any insurgents who had “no blood on their hands” as the first step in a peace initiative designed to save the nation of 46 million ― whose Crimea peninsula was annexed by Russia in March ― from fracturing further along ethnic lines.

“I am assuming the presidency in order to preserve and strengthen Ukraine’s unity,” Poroshenko said in a confident address to parliament that symbolically alternated between Russian and Ukrainian.

“The citizens of Ukraine will never feel the blessing of peace and security until we resolve our relations with Russia,” he added.

But Poroshenko also said he would never accept Russia’s seizure of Crimea or attempts to divert Ukraine’s pro-European course.

The new Ukraine leader may meet a Russian envoy on Sunday for the first round of talks aimed at resolving the crisis between the two neighbours.

U.S. Secretary of State John Kerry, who was in France Saturday for World War II commemorations, congratulated Poroshenko on his inauguration.

“While there is a great deal of work ahead, the path forward President Poroshenko has proposed would lead to a de-escalation of tensions. Ukraine can be a bridge between Russia and the West marked by strong economic relationships with both sides,” he said.

Kerry urged Putin “to engage directly” with Poroshenko, halt the flow of arms, and “take steps to bring an end to the violent acts of Russian separatists in eastern Ukraine.”

U.S. Vice President Joe Biden attended Poroshenko’s inauguration, and the White House said Biden had pledged an additional $48.0 million in assistance aimed at helping the new leader’s team protect Ukraine’s eastern border and reduce its costly dependence on Russian gas imports.

But separatist commanders whom the West accuses Russia of openly backing dismissed Poroshenko’s presidency as illegitimate.

Separatists in the self-proclaimed “Republic of Lugansk” called on the new Ukrainian president to withdraw his army from the east.

“Negotiations cannot begin until the retreat of the occupying troops from our territory,” said the “president” in Lugansk, Valery Bolotov, in a statement to the press.

Poroshenko is one of Ukraine’s more experienced politicians, who held senior cabinet posts under both the Western-leaning government that followed Ukraine’s 2004 Orange Revolution and the Moscow-friendly leadership of ousted president Viktor Yanukovych.

That pragmatic approach has instilled hope among many Ukrainians that he will be able to resolve an eight-week secessionist drive by pro-Russian militants in the eastern rust belt that has claimed 200 lives and grown even more violent since his election.

Poroshenko ― who has vowed to give up direct ownership of his holdings to avoid a conflict of interest ― must also address a two-year recession and endemic corruption that has turned Ukraine into one of Europe’s poorest countries and has fed broad public discontent.

He embarked on his most urgent assignment Friday by shaking hands with Putin on the sidelines of D-Day commemorations in Normandy that were haunted by the spectre of an outright civil war breaking out on the European Union’s eastern edge.