After six months of offering only carrots, president's threat of big stick seems too little, too late

After Donald Trump required six months to conclude that Vladimir Putin may not be a kindred transactional authoritarian leader but an ideological nationalist seeking the return of what "belongs to Russia", the deadline he set for the Russian president to agree a Ukraine ceasefire or face US sanctions on oil exports arrives tomorrow.

- Patrick Wintour

What Trump - who some had claimed was a Russian asset - does next to punish Putin could define his presidency. It is a remarkable turnaround for the US president and one that seasoned Trump watchers such as Michael McFaul, former US ambassador to Russia, admit they had never expected.

Only months ago the debate was exclusively about what further inducements and sanction relief Trump would offer Putin to end the fighting. His administration has not introduced any sanctions against Russia, compared with at least 16 sets of actions in every six-month period back to February 2022, according to a report submitted to the Senate banking committee by top Democrats this week. Instead, in the middle of July, Trump set Putin a 50-day deadline then cut weeks off it.

Matthew Whitaker, US ambassador to Nato, said on Tuesday: "Secondary sanctions and tariffs against China, India, and Brazil, which buy Russian oil, are the obvious next step in an attempt to stop the conflict." Yet as the deadline approaches, there is a lingering scepticism about how far Trump will go. He has dispatched his special envoy, Steve Witkoff, to Moscow for the fifth time for last-minute talks, and on Friday Trump admitted he did not think sanctions would have much impact since Russians are "wily characters and they're pretty good at avoiding sanctions".

He has also given himself maximum room for political manoeuvre by ensuring the US Senate did not pass legislation before its summer recess that would have empowered him to slap bone-crushing 500% tariffs on exports from countries that import Russian oil, principally India, China, Brazil and Turkey.

Trump had argued that the congressional legislation was unnecessary since he can act through executive orders, mentioning instead 100% tariffs on economies that import Russian oil - a huge number, even if lower than the 500% floated by the Republican senator Lindsey Graham.