KIEV (AFP) – Ukraine’s new Western-backed president faced pressure on Tuesday to negotiate with top rebel commanders after a surprise turnabout in which the insurgents agreed to a truce and talks on ending their pro-Russian uprising.

The prominent head of the self-declared Donetsk People’s Republic on Monday unexpectedly reversed his firm rejection of President Petro Poroshenko’s peace overtures by agreeing to a ceasefire that would last until Friday morning.

“We hope that during the period in which both sides halt fire, we will be able to agree and begin consultations about holding negotiations about a peaceful settlement to the conflict,” Oleksandr Borodai said after a meeting with Russia’s ambassador to Kiev and an OSCE envoy.

The decision put the onus on Poroshenko to reconsider his refusal to talk directly to rebels implicated in nearly three months of violence that have killed almost 400 people in Ukraine’s Russified rustbelt.

The Russian-border regions of Donetsk and Lugansk — home to seven million people as well as Ukraine’s crucial coal and metals industry — were overrun in early April by gunmen who proclaimed their independence from Kiev the following month.

The rebel commanders in Lugansk have not yet publicly joined Borodai’s talks offer and the Ukrainian military reported more sporadic violence overnight.

The spokesman of Ukraine’s “anti-terrorist operation” said a government roadblock had come under attack outside the Donetsk rebel stronghold city of Slavyansk. He added that there were also small exchanges of fire near the Russian border in the Lugansk region.

“Ukrainian servicemen suffered no losses,” Vladyslav Seleznyov wrote in a Facebook post.

Kiev has reported no casualties since Poroshenko ordered his forces to halt fire for a week on Friday night.

– Western sanctions threat –

Poroshenko has been lobbying world leaders to follow through with their threat to unleash devastating economic sanctions against Russia should President Vladimir Putin fail to immediately end his perceived military and diplomatic backing for the insurgents.

Putin was expected to face more Western pressure in Vienna on Tuesday when he meets his Austrian counterpart Heinz Fischer and Switzerland’s Didier Burkhalter — the current head of the Organization for Security and Cooperation in Europe (OSCE).

Poroshenko for his part was due to host German Foreign Minister as part of Europe’s ongoing effort to demonstrate support for Kiev’s embattled leaders.

Ukraine’s president will also sign a historic EU trade pact on Friday that crowns his May 25 election promise to make the decisive move westward — one strongly resisted by Russia and that lies at the heart of the current unrest.

Poroshenko’s office said he told US Vice President Joe Biden on Monday night that the rebels’ ceasefire “must be accompanied by the release of hostages and a sealing of the border to halt the entry into Ukraine from Russia of mercenaries, weapons and drugs.”

“Poroshenko stressed that now, Russia must demonstrate real steps forward,” his office said in a statement.

The European Union warned after a meeting of foreign ministers on Monday that it expected to see action from Putin “within days.”

The White House said US President Barack Obama also told Putin by phone on Monday that Russia would face new sanctions if it failed to stop the flow of weapons into Ukraine.

Some analysts believe that Putin is still smarting from the sudden loss of an ally in Kiev — ousted by pro-EU protesters in February — who could have brought Ukraine into a new alliance of post-Soviet nations being assembled by the Kremlin.

The subsequent flow of heavy weapons and gunmen across the porous border into eastern Ukraine seem to indicate that the Kremlin is — at the very least — turning a blind eye to local Russian officials and military commanders’ efforts to support the insurgents.

And Putin’s order on Saturday for Russian forces from the Volga to western Siberia to conduct snap military drills also suggests that he wants to keep Poroshenko’s government unsettled in order to maintain influence in eastern Ukraine.

But the Kremlin chief seems equally determined to avoid steps that could trigger broader sanctions and deal a further blow to a Russian economy that is already teetering on the edge of a recession.