Ekaterina Len ( R) stands in her house destroyed by the fighting between Ukrainian forces and the pro-Russian militants in the eastern Ukrainian city of Slavyansk on May 20, 2014. Image Credit: AFP

Kiev: The United States piled the pressure on Russia Wednesday over its actions in Ukraine, where the authorities are mobilising tens of thousands of police for a presidential vote in the face of a bloody insurgency gripping the east.

Vice President Joe Biden threatened further sanctions on Moscow if it disrupts Sunday’s presidential ballot, being viewed as crucial to prevent all-out civil war on Europe’s doorstep.

In a key step demanded by the West to ease tensions, Russia said its troops were packing up and moving back from the Ukrainian border, but also again demanded that Kiev halt its offensive against the pro-Moscow separatists fighting in the east.

Washington and Nato have so far said they have seen no sign of any pullback, although Ukraine’s border guard service said Tuesday there was no visible Russian troop activity within 10 kilometres of its territory.

“If Russia undermines these elections on Sunday, we must remain resolute in imposing greater costs,” Biden told reporters in Romania.

“All countries should use their influence to promote a stable environment for Ukrainian citizens to cast their ballots freely.”

Ukraine said it plans to deploy more than 55,000 police and 20,000 volunteers to ensure security on polling day.

The interior ministry’s public order director Andriy Chaliy conceded the “threat of Russia’s aggression and the actions of separatists in the east” posed a threat to the vote.

Biden also praised Kiev’s pro-Western government for its “steps to engage Ukrainians, from all parts of that country, in the east and the south, on issues of constitutional reform”.

The government which took power in the aftermath of the bloody protests that forced out the pro-Kremlin regime in February is holding a new round of so-called national unity talks on Wednesday.

The discussions are part of a peace roadmap sponsored by the pan-European OSCE security body, but two previous sessions failed to make any progress, with Kiev pointedly refusing to invite the armed separatists now in control of swathes of the eastern coal and steel belt.

Ukraine’s parliament also agreed Tuesday to put a conciliatory measure up for a future vote that would grant more powers to the regions and ensure that the right to speak Russian in public institutions is enshrined in the constitution - among key demands of the rebels.

Some separatist leaders are pushing for the eastern regions to become part of Russia, emboldened by Moscow’s annexation of the Black Sea Crimean peninsula in March.

The United States and Nato have sent troops to Poland and the three tiny Baltic nations to calm jitters about Russian troops possibly not only overrunning Ukraine but also pushing further into Europe in a bid to reclaim ex-Soviet satellite states.

The Pentagon announced Tuesday it was sending in a guided missile cruiser to the Black Sea, saying it had not seen any “withdrawal activity” by Russian troops.

“They are still in the tens of thousands,” Pentagon spokesman Rear Admiral John Kirby told reporters.

Moscow said Wednesday its military units have been dismantling their field camps neighbouring Ukraine and loading up their equipment to head back to their permanent bases.

But the sabre-rattling is showing no signs of a let-up.

Russian Prime Minister Dmitry Medvedev said Tuesday that Moscow and the West were still “slowly but surely” approaching a second Cold War.

And Biden blasted Russia’s seizure of the Crimean peninsula, saying: “Europe’s borders should never again be changed at the point of a gun”.

Both Kiev and its Western allies see the election - backed only grudgingly by Moscow - as a chance to unite the culturally splintered nation and win more legitimacy in the Kremlin’s eyes.

The front-runner, chocolate baron Petro Poroshenko, has pledged to find a negotiated solution to the crisis and rebuild ties with Ukraine’s former masters in Moscow.

The UN estimates that around 130 people have died since the insurgency erupted last month in the Donetsk and Lugansk regions, where rebels have declared sovereignty after independence referendums denounced in Kiev and the West as illegal.

In nearly six weeks since launching its “anti-terrorist” offensive, Ukraine’s military has so far failed to dislodge the rebels and suffered several humiliating setbacks.

But in a move that some say could turn the tide against the rebels, Ukraine’s richest man Rinat Akhmetov has condemned the rebellion in his industrial power base.

“People are tired of living in fear and terror,” said Ahkmetov, a coal and steel magnate who has sought to rally workers in their millions to stand up to the separatists.