Ukrainian president Volodymyr Zelenskiy and Russian counterpart Vladimir Putin will keep a close eye on events in London and Washington this week as they prepare to meet for the first time next Monday.
The two leaders will join French president Emmanuel Macron and German chancellor Angela Merkel in Paris for so-called Normandy format talks aimed at ending more than five years of war in eastern Ukraine.
Kiev and Moscow say they hope for progress at the Élysée Palace despite their deep differences, but the meeting could be buffeted by turbulence from a potentially fractious Nato summit this week and a vote on impeachment proceedings against US president Donald Trump over his dealings with Ukraine.
The House of Representatives' intelligence committee is expected to approve the transfer of the impeachment inquiry to its judiciary committee on Tuesday, despite Mr Trump's furious denials that he sought to withhold military aid from Ukraine until it agreed to investigate political rival Joe Biden and his son.
Tense affair
Mr Trump will be at the Grove hotel outside Watford on Tuesday and Wednesday for a summit of Nato leaders, which promises to be a tense affair even without the likely fallout from political developments across the Atlantic.
Ukraine has relied on Nato members' support since Russia seized Crimea and fomented war in the Donbas region in 2014, but now it feels the ground shifting just as Mr Zelenskiy seeks to negotiate with the Kremlin from a position of strength.
Mr Macron alarmed France's allies last month by saying Nato was suffering "brain death" and questioning the group's collective security guarantee amid what he called indications that Washington was "turning its back" on Europe.
After talks with Nato secretary-general Jens Stoltenberg last week, Mr Macron reiterated his recent calls for re-engagement with Russia, which has been hit by western sanctions over its aggression against Ukraine.
“Is our enemy today Russia? Or China? Is it the goal of Nato to designate them as enemies? I don’t believe so. Our common enemy today in Nato is terrorism,” he declared.
“A new architecture of confidence and security in Europe will stem from clarifying our relations with Russia while stating conditions,” he added.
Mr Macron insisted that France would be "uncompromising" in defending its allies and that only a "lucid, robust and demanding" stance towards the Kremlin would work, but he also argued for a new approach to Mr Putin.
“Has the absence of dialogue with Russia made the European continent any safer? I don’t think so,” he said.
Fuel tension
Mr Macron's emollient words remind some people in Ukraine and elsewhere in eastern Europe of Barack Obama's "reset" of US-Russia relations when he became president after Moscow's 2008 invasion of Georgia, and which led nowhere.
The French leader’s overtures to the Kremlin could also fuel tension between Paris and Berlin, which Ukraine sees as joint defenders of its interests in the Normandy talks in the face of Russian power.
“I understand your desire for disruptive politics,” Dr Merkel reportedly told Mr Macron last month.
“But I’m tired of picking up the pieces. Over and over, I have to glue together the cups you have broken so we can then sit down and have a cup of tea together.”
If Mr Trump – a fierce Nato critic who has made Ukraine his personal quagmire – also smashes the crockery at this week’s Nato summit, then Mr Putin will surely relish meeting the inexperienced Mr Zelenskiy amid western discord.
"One way or another, Putin and Zelenskiy will talk," Kremlin spokesman Dmitry Peskov said on Sunday.
“One can assume that it won’t be a meeting to lead everything to a dead end, but rather to really try to find some solutions.”