Petro Poroshenko's announcement comes after a phone conversation he had with the Russian president, Vladimir Putin

The Ukrainian president, Petro Poroshenko, said he would order a ceasefire to begin at lunchtime on Friday if peace talks that are planned to be held in Minsk, Belarus, are confirmed.

Speaking on the sidelines of a Nato summit in Wales, Poroshenko said: "At 2pm local time [11am GMT] 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."

The announcement comes after a phone conversation between Poroshenko and Vladimir Putin on Wednesday. The Russian president later released a seven-point "peace plan" for eastern Ukraine.

On the ground in east Ukraine, a rebel armoured column moved from the town of Novoazovsk, seized last week, in the direction of Mariupol, a major port city that the Ukrainians have said they will defend against any assault. Shelling was audible on the outskirts of town on Thursday afternoon, though there were no immediate signs of a full-scale assault on the city.

There were also reports that Ukrainian forces had shelled the outskirts of Donetsk, the main rebel stronghold, overnight. Kiev says the reverse in fortunes in recent weeks has come as a result of direct Russian military intervention. Russia has denied all claims that its soldiers are operating in Ukraine.

The Russian foreign minister, Sergei Lavrov, said on Thursday he hoped both Kiev and the rebels would sign up to Putin's peace plan, which would essentially freeze the conflict. Ukrainian authorities are unlikely to accept any settlement that involves recognising rebel control over territory, but are aware that Kiev's forces have suffered such losses in the past fortnight that they cannot go on fighting.

Poroshenko said on Wednesday morning that he had agreed a "permanent ceasefire" in the east but later backed away from the statement, while other top Ukrainian officials said there could be no talk of peace while Russian troops were operating in Ukraine.

Lavrov blamed Kiev's desire to win back control militarily on influence from Washington.

"The surge in anti-Russian rhetoric that we have seen exactly when there is a very active effort to seek a political solution, shows that the party of war in Kiev has active external support, in this case from the United States," said Lavrov at a press conference.