Russian President Vladimir Putin has asked Russia's upper house to revoke the right it had granted him to order a military intervention in Ukraine in defence of Russian-speakers there.
The step seems certain to be welcomed by the West as a sign Russia could be ready to help engineer a settlement in Ukraine's largely Russian-speaking east.
A pro-Russian uprising against the Kiev government began in the region in April. Mr Putin's spokesman said the move was aimed at assisting the fledgling peace talks to end the conflict.
Ukrainian President Petro Poroshenko called it a "first practical step" following Mr Putin's statement of support last weekend for Mr Poroshenko's peace plan for eastern Ukraine.
In the 1 March resolution, the Federation Council had granted Mr Putin the right to "use the Russian Federation's Armed Forces on the territory of Ukraine until the social and political situation in that country normalises".
That resolution, together with Russia's annexation of Crimea from Ukraine, helped to send East-West relations to their lowest ebb since the Cold War.
The tension led the United States and Europe to impose sanctions on Russia.
European Union foreign ministers yesterday held out the prospect of further sanctions if Russia did not do more to support a peace process in eastern Ukraine, and also asked it to revoke the 1 March resolution.
Since then, rebels in eastern Ukraine have agreed to a temporary ceasefire to give time for peace talks in a forum where Russia is represented alongside the Kiev government and the Organisation for Security and Cooperation in Europe.
"The president has filed a proposal to the Federation Council on cancelling ... the resolution on the use of Russia's Armed Forces on the territory of Ukraine," the Kremlin said in a statement on its website.
Federation Council Speaker Valentina Matviyenko said the chamber would discuss Mr Putin's request tomorrow.
The deputy head of the chamber's international affairs committee, Andrei Klimov, said he expected the resolution to pass, according to the RIA Novosti agency.
Ukrainian helicopter shot down near Slaviansk
Nine people were killed when a Ukrainian helicopter was shot down by pro-Russian militants, a military spokesman said.
The helicopter was carrying technicians who had been installing equipment to monitor violations of a peace plan in the east of the country.
The Mi-8 cargo helicopter was struck by a rebel missile near Slaviansk in eastern Ukraine in the early hours of this morning, government forces spokesman Vladyslav Seleznyov said.
"There were 9 people on board. According to preliminary information ... all those on board were killed," Mr Seleznyov said on his Facebook page.
The nine dead included a three-man crew.
"The (rebel) fighters, having fired the rocket, hid in the nearby village of Bylbasovka," he said.
The incident took place just hours after pro-Russian separatists last night announced a ceasefire until 27 June to match a week-long truce by government forces which has been ordered by President Poroshenko.
It was the second time a helicopter has been brought down by rebel fire from Slaviansk, a separatist stronghold.
On 30 May,rebels there also downed a military helicopter killing 14 servicemen, including one general.
Claims shots fired after ceasefire
Earlier, Ukrainian government forces accused pro-Russian separatists of firing on Ukrainian military checkpoints in several parts of the east last night despite the ceasefire declared by the rebels.
No sustained fighting was reported in the incidents and no casualties were reported on the Ukrainian side.
"[Separatist] fighters are not ceasing to shoot at the positions of Ukrainian forces," Mr Seleznyov, said on his Facebook page this morning.
He said rebel militia, using grenade-launchers and mortar, carried out attacks on a government military post near the rebel-controlled town of Slavyansk.
They used small arms in an assault on another post further east towards the border with Russia, Mr Selznyov said.
He said Ukrainian government forces had not been involved in any military action in line with the ceasefire announced by President Poroshenko last Friday.
"I cannot say whether the separatists have violated or not violated [the ceasefire], but the facts speak for themselves - yesterday during the day and in the evening they fired on our positions," Mr Seleznyov told Reuters.