Kiev also appeared to ratchet up the pressure by banning entry to its territory for all Russian males aged 16 to 60, airline Aeroflot announced just as negotiations between the foreign ministers of Russia, the United States, the European Union and Ukraine took place.

But in a sign that the talks could be yielding some results, negotiations that were originally due to end mid-afternoon dragged out behind closed doors as the four parties worked on a joint statement acceptable to all.

Ukraine appears close to rupturing in two as pro-Kremlin separatists have taken over parts of the restive southeastern industrial heartland — militants Kiev says are being supported by Russia to destabilise the former Soviet state.

Putin categorically denied this Thursday, warning Ukraine was plunging into the “abyss” just hours after three separatists were killed in a gunbattle with troops, and stressing he hoped not to have to use his “right” to send Russian troops into its western neighbour.

“I very much hope that I am not obliged to use this right and that through political and diplomatic means we can solve all the acute problems in Ukraine,” he said in his annual televised phone-in with the nation, in a signal the option was on the table.

The upper house of parliament on March 1 authorised the Russian leader to send troops into Ukraine after pro-Kremlin president Viktor Yanukovych was ousted, and Moscow later went on to annex Ukraine’s Russian-speaking Crimean peninsula.

Russia has now massed tens of thousands of troops at the border. But it denies backing the separatists currently wreaking havoc in the southeast and has warned Kiev’s untested new leaders not to use force against them.

While Kiev launched a much-hyped military operation against separatists earlier this week, the action ended in failure when the insurgents humiliated Ukrainian troops by blocking them and seizing six of their armoured vehicles.

A concerned NATO promptly announced it was deploying more forces in eastern Europe and urged Russia to stop “destabilising” Ukraine, which has been in turmoil since the ouster of Yanukovych in February and now threatens to split between its EU-leaning west and Russian-speaking east

– A ray of hope? –

The situation in Ukraine has emerged as the biggest East-West crisis since the end of the Cold War.

Each side came to the Geneva talks armed with a very specific set of demands, in what was likely to make negotiations between Russia’s Sergei Lavrov, Ukraine’s Andriy Deshchytsya, US Secretary of State John Kerry and EU foreign policy chief Catherine Ashton very tough.

The West and Kiev aim to get Moscow to demobilise the militias, and the United States warned Moscow on Wednesday that it risked fresh sanctions unless it made concessions.

Ukraine’s Security Service said it was detaining 10 “Russian spies” arrested over the past six weeks on suspected missions to stir up unrest in the country.

But Moscow categorically denies having dispatched elite special forces to Ukraine to stir unrest, despite Kiev intelligence saying the same Russian agents who oversaw the seizure of Crimea last month are now coordinating the unrest in the southeast.

Instead, Russia blames Kiev’s interim leaders — installed by Ukraine’s parliament in February after the overthrow of Yanukovych following months of protests — for pushing the country dangerously close to a civil war.

Still, as the Geneva talks dragged on well past a planned mid-afternoon press conference, a ray of hope emerged as a Western official who wished to remain anonymous said the four parties were “working on a joint statement about the path forward”.

– Tackling Russian ‘aggression’ –

The United States and European Union have already imposed punitive sanctions on key Russian and Ukrainian political and business officials, including members of Putin’s inner circle.

But if the meeting ends in failure, Western countries are prepared to ramp up sanctions that could hurt Russia’s already struggling economy.

The European Parliament said the European Union should act “against Russian firms and their subsidiaries, especially in the energy sector, and Russia’s EU assets”.

Nevertheless, the European Union said it had agreed to hold talks with Russia on its gas supplies to Europe through Ukraine, warning Moscow its reliability as an energy source was at stake.

The announcement came even as Putin ramped up pressure on Ukraine by setting a one-month deadline for Kiev to settle its debt for gas imports from Russia.

In the meantime, Kiev disbanded the army unit that lost the six armoured vehicles and announced it was considering bringing back conscription in the face of Russian “aggression.”

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