Ukraine, Rebels Back Peace Plan, Ceasefire from Friday

The breakthrough came after a week in which the pro-Moscow separatists scored major victories with what NATO says is the open support of thousands of Russian troops.

Speaking on the sidelines of a NATO summit in Wales, Poroshenko said the ceasefire would be conditional on a planned meeting going ahead in Minsk on Friday of envoys from Ukraine, Russia and Europe's OSCE security watchdog.

"At 1400 local time on Friday, provided the (Minsk) meeting takes place, I will call on the General Staff to set up a bilateral ceasefire and we hope that the implementation of the peace plan will begin tomorrow," he told reporters.

Alexander Zakharchenko, head of the main rebel Donetsk People's Republic, said in a statement his men would also order a ceasefire, from one hour later, provided that Kiev's representatives signed up to a peace plan at the Minsk meeting.

There have been local agreements to hold fire, for example during the recovery of bodies from a Malaysian airliner shot down over rebel territory in July, but Thursday's announcements were the first time the two sides have called for a full truce.

Rebels still expressed skepticism. Oleg Tsaryov, a senior rebel official, told Reuters the separatist truce would depend on the government providing guarantees, "because in the past we had some ceasefire agreements Poroshenko didn't honor".

A source close to Zakharchenko said government forces bombarded Donetsk within 15 minutes of Poroshenko's announcement of the ceasefire plan: "We'll see how the talks go tomorrow, but it won't be easy. All this talk of truce amid more and more shelling."

The announcements come a day after Russia's President Vladimir Putin put forward a seven-point peace plan, which would end the fighting in Ukraine's east, bring in outside monitors and aid, while leaving rebels in control of their territory.

To keep the pressure up on Russia, a White House official attending the NATO summit said the US was preparing a new round of economic sanctions, but progress towards a truce could halt new European financial sanctions that EU leaders had been expected to agree on Friday. French President Francois Hollande said the decision on the sanctions package would depend "on the coming hours".

German Chancellor Angela Merkel, however, warned that while NATO members wanted a political solution and would talk to Russia about this, "We're also prepared to lend weight to our political demands by imposing further sanctions".

There is no sign of a halt in fighting in the east, where rebels have rapidly advanced in the past week, backed by what Kiev and NATO say is the support of thousands of Russian troops with artillery and tanks. Moscow denies its troops are there.