Western allies should learn in the next few days if their punishing sanctions on Russia have softened its stance on Ukraine enough to justify lifting the drag on Europe's increasingly fragile economic recovery.
Recent signals from Moscow have been encouraging.
Russian President Vladimir Putin on Saturday ordered 17,600 troops performing drills near the Ukrainian border back to their bases. And the number of weekend attacks by pro-Kremlin insurgents in the former Soviet state's separatist east sharply fell.
Firmer confirmation of a rapprochement may come on Tuesday in Paris when US Secretary of State John Kerry confronts Russian Foreign Minister Sergei Lavrov.
But the final answer may only emerge after a likely meeting in Milan on Friday between Putin and Ukrainian President Petro Poroshenko -- their third since Kiev's switch of allegiance this year from Moscow to the West.
"I am not expecting these negotiations to be easy," Poroshenko said on Saturday. "But I am an optimist."
At stake will be the fate of a shaky Ukrainian truce deal that -- after the loss of 3,400 lives -- has calmed some fighting but failed to thwart rebel plans to hold their own elections on November 2.
Hanging in the balance are the punitive EU and US restrictions on Russia that have prompted a sort of trade war and contributed to Germany's biggest drop in exports since the global financial crisis of 2009.
- Frosty Putin-Poroshenko relations -
The last meeting between Poroshenko -- a billionaire chocolatier who manned the barricades during bloody protests that toppled a Kremlin-backed president in February -- and Putin in August ended on a frosty note.
Those Minsk talks however helped pave the way for a September 5 peace pact and a subsequent truce agreement designed to create a buffer zone along the front line and grant the insurgents limited autonomy within Ukraine.
But neither side has pulled back their big guns or halted all fire. Militias across the Russian-speaking rustbelt still attack Ukranian forces, and the number of civilians killed every day by stray shells and rockets is nearing that seen at the height of the six-month war.
They also failed to convince Poroshenko that Moscow had not orchestrated the uprising to punish Kiev for its decision to ditch a Kremlin-led trade bloc, the Eurasian Economic Union, and sign a landmark agreement with the European Union instead.
"It is hard to overemphasise Russia's role in ensuring peace," Poroshenko said ahead of his faceoff with Putin.
The 49-year-old Ukranian leader added that Russia's suspension of gas deliveries in the runup to the winter heating season will be "one of the main issues" discussed in Milan.
But analysts note that Poroshenko has little to offer in return and instead must rely on friends such as German Chancellor Angela Merkel and US President Barack Obama to convince Putin to reverse course.
"Putin does not view Poroshenko as an equal partner," said Oleksandr Sushko of Kiev's Institute for Euro-Atlantic Cooperation.
- Kerry weighs Russian sanctions -
Putin has made some overtures suggesting a degree of goodwill to relieve the worst East-West standoff since the 1989 fall of the Berlin Wall.
His decision to call back a bulk of Russia's troops parked near Ukraine followed Moscow's postponement of retribution it threatened after being effectively cut off from Western money markets in July.
Those measures have forced Russia's biggest banks and oil company to appeal for multi-billion rescues that should further limit the government's ability to meet its social commitments and invest in future growth.
They also threaten to tip Russia into recession and assure that growth -- slowing even before Moscow and the West dug in their heels over Ukraine -- remains anaemic through the remaining four years of Putin's third term.
Lavrov is expected to impress on Kerry Moscow's main argument in favour of sanctions relief: that the pain they cause European economies more closely intertwined with Russia's will soon impact US growth.
"Everyone is talking on the sidelines about... their desire to get the sanctions behind them because obviously they hinder their own development," Russian Finance Minister Anton Siluanov said during a break on Saturday in global economic talks in Washington.
But political analyst Volodymyr Gorbach cautioned that expectations in Kiev going into the Kerry-Lavrov meeting were low because Russia was ultimately unwilling to see Ukraine slip out of its orbit for good.
"Russian-US relations are not likely to improve," said Gorbach.