Moscow promised on Saturday to resume shipping coal and provide electricity to Ukraine for the first time in three years despite Kiev's failure to guarantee energy supplies to Russian-occupied Crimea.
Russian President Vladimir Putin's unexpected decision was announced just a day after Ukraine upped pressure on the breakaway Black Sea peninsula by severing all its train and bus ties with the mainland.
The Kremlin did not link Putin's "discounted" energy offer to Kiev's increasingly punitive approach to the renegade region of 2.3 million.
But Russia's public support in Crimea -- essential in the face of global condemnation of its March annexation -- depends heavily on Putin's ability to improve living conditions in the long-neglected summer resort.
A top Kiev media outlet reported that Ukrainian President Petro Poroshenko had used the Crimea travel ban as a bargaining chip in his energy negotiations with the Kremlin.
Both Moscow and Kiev refused to disclose the terms of the coal and electricity deal.
"Considering the critical situation with (Ukranian) energy supplies, Putin decided to start these shipments despite the lack of prepayments," Kremlin spokesman Dmitry Peskov told the TASS new agency.
"This demonstrates President Putin's political will to provide real support to Ukrainians, especially on the eve of New Year."
Ukraine's eight-month separatist uprising in the Russian-speaking industrial east has shuttered many of the region's huge coal mines and left the former Soviet republic's antiquated boilers desperately short of fuel.
The energy crunch has been compounded by the temporary shutdown one month ago of southern Ukraine's Zaporizhia Nuclear Power Plant -- Europe's largest and the fifth most powerful in the world.
Russian Deputy Prime Minister Dmitry Kozak said Moscow would start by sending 500,000 tonnes of coal a month "to help (Ukraine) solve the problem of reliable energy supplies for Crimea."
Kozak said those volumes could double if a corresponding agreement was signed.
But he also admitted that Kiev had failed to guarantee that any of these supplies would reach the Russian-controlled peninsula -- suffering from periodic power cuts for most of the past week.
"No agreement concerning Crimea has been signed to date," Kozak told the Rossiya 24 state news channel.
Yet he implied that Moscow had received Kiev's private commitment to keep Crimea's lights on and homes heated throughout the difficult winter months.
"We have taken their word for it, as they say," the Russian minister said.
- 'Crimean factor' -
Crimea has been one of many Ukrainian regions to suffer rolling blackouts this month.
Ukraine was forced to delay providing winter heating to homes for several weeks because of a months-long interruption of Russian natural gas shipments that was only resolved at the end of October.
And its attempt to strike a massive coal delivery deal with South Africa ended in a corruption scandal that saw a top Ukrainian official jailed and later placed under house arrest.
The respected editor of Kiev's Ukrainska Pravda news site reported that Poroshenko used "the Crimean factor" to strengthen his bargaining position during three weeks of arduous energy negotiations with Russia this month.
"This explains the power cuts to the peninsula and today's transportation blockade," Sevgil Musaieva-Borovyk wrote in a blog post.
"And Russia made concessions," Musaieva-Borovyk wrote.