Ukraine's President Petro Poroshenko says he has agreed with Russian President Putin by phone on a "ceasefire process" for the east.
His office initially reported that a "permanent ceasefire" had been agreed but later revised its statement.
The Kremlin stressed Putin had not agreed to a ceasefire as Russia was not party to the conflict.
US President Barack Obama has expressed solidarity with Baltic member-states of Nato on a visit to Estonia.
He is in the Estonian capital Tallinn with President Toomas Hendrik Ilves of Estonia and the leaders of Latvia and Lithuania, all former Soviet states which joined Nato a decade ago.
A Nato summit opening in Wales on Thursday is expected to back plans for a rapid response force.
More than 2,600 civilians and combatants have been killed and more than a million people have fled their homes since fighting erupted in eastern Ukraine in April, when pro-Russian separatists there declared independence.
Russia has denied accusations by the West and the Ukrainian government that it is sending troops and military equipment over the border to support the separatists, who recently gained the upper hand against government forces.
The earlier version of the statement on the Ukrainian presidential website read: "Their conversation resulted in agreement on a permanent ceasefire in the Donbass region [the regions of Donetsk and Luhansk]."
However, this has now been changed to: "Their conversation resulted in agreement on a process for ceasing fire in the Donbass region."
The statement adds that the two presidents "reached a mutual understanding on steps leading to peace".
In its statement (in Russian), the Kremlin said a phone conversation had taken place on Wednesday between the two presidents in which their points of view had "coincided significantly" on possible ways to end the crisis.
Putin's spokesman, Dmitry Peskov, clarified for Russian news agency Ria-Novosti: "Putin and Poroshenko did not agree a ceasefire in Ukraine because Russia is not party to the conflict, they only discussed how to settle the conflict."
A rebel spokesman told the same agency the rebels did not believe Poroshenko was in complete control over Ukrainian forces in the east.
At a news conference with President Ilves, Obama said Estonia would "never stand alone".
Obama is also due to meet Lithuania's Dalia Grybauskaite and Latvia's Andris Berzins.
The BBC's Europe editor Gavin Hewitt says the three former Soviet states have been unsettled by President Vladimir Putin's insistence that Russia has a right to intervene to defend the interests of Russian speakers.
The White House said Obama would use his trip to Estonia, where about 25% are ethnic Russians, to make it clear that it is "not okay for large countries to flagrantly violate the territorial integrity of their smaller neighbours".
In another development, the death of a Russian photojournalist in Ukraine last month has been confirmed.
Rossia Sevodnya news agency photojournalist Andrei Stenin was killed on 6 August in a Ukrainian government ambush on a convoy of rebels and refugees near Donetsk, Russia's Investigative Committee announced. His charred remains have only now been identified.