Rishi Sunak is promising to "call out Putin's regime" at a gathering of world leaders in Indonesia.
The prime minister is travelling to Bali on Sunday afternoon for a summit of the G20 – the world's biggest economies.
British officials had prepared for this get-together assuming Russia's president would be there.
The prime minister was expected to join other world leaders in condemning Vladimir Putin to his face.
But Moscow said last week he wouldn't be attending and the Kremlin would be sending Russia's foreign minister, Sergei Lavrov, instead.
So the words of anger will be directed at him.
Speaking before setting off for Indonesia, the prime minister said: "Putin's war has caused devastation around the world – destroying lives and plunging the international economy into turmoil.
"This G20 summit will not be business as usual. We will call out Putin's regime, and lay bare their utter contempt for the kind of international cooperation and respect for sovereignty forums like the G20 represent."
The G20 is a hotchpotch of countries with little in common beyond big economies.
An economic forum whose members have been hammered, economically, by one of their own, Russia.
So the backdrop is awkward, to say the least.
There won't even be one of the basic diplomatic niceties of these gatherings this time, what is known as the family photo, where the leaders pose for a group picture.
The other leaders refuse to be seen smiling in the presence of Russia.
Recent precedent suggests another usual staple of these affairs, what is known as a communique, a set of agreed conclusions published at the close of the summit, probably won't happen either.
Almost three weeks into the job, this is Mr Sunak's second overseas trip as prime minister, after last week's dash to the COP27 climate summit in Egypt.
He managed to see a good number of fellow European leaders in Sharm el-Sheikh.
The trip to Bali will mean he can meet plenty from the Indo-Pacific region, a part of the world the government has been increasingly focused on since Brexit.
And, perhaps, a first chance to meet US President Joe Biden.
Meanwhile, back home, as Laura Kuenssberg writes, the Chancellor Jeremy Hunt will continue preparing what is called the Autumn Statement, a budget in all but name, to be delivered on Thursday, just hours after the prime minister gets back home.
Downing Street is seeking to frame both the summit and the Autumn Statement as responses to the same shock: the consequences of the war in Ukraine.
A desperate global economic situation, as they describe it, with big domestic implications, that they seek to be trusted to grapple with, after the chaos of the Liz Truss administration.
But a fractious summit followed by what many will see as a bad news Budget won't make for an easy week for Mr Sunak.
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