Ukrainian President Volodymyr Zelenskiy, who was not invited to the talks, and his European allies fear Trump might sell out Ukraine by essentially freezing the conflict and recognising - if only informally - Russian control over one-fifth of Ukraine.
Both Trump and Putin are seeking wins from their first face-to-face talks since Trump returned to the White House.
Trump, who casts the war as a "bloodbath" fraught with escalatory risk, is pressing for a truce in the three-and-a-half-year-old war that would bolster his credentials as worthy of the Nobel Peace Prize.
For Putin, the summit is already a big win as he can use it to say that years of Western attempts to isolate Russia have unravelled and that Moscow has retaken its rightful place at the top table of international diplomacy.
The summit, the first between a US and Russian leader since 2021, will begin at 11am on Friday (5am on Saturday AEST).
Trump, who once said he would end Russia's war in Ukraine within 24 hours, conceded on Thursday it had proven a tougher nut to crack than he had thought.
He said if Friday's talks went well, quickly setting up a subsequent three-way summit with Zelenskiy would be even more important than his encounter with Putin.
A source acquainted with Kremlin thinking said there were signs Moscow could be ready to strike a compromise on Ukraine given Putin understood Russia's economic vulnerability and costs of continuing the war.
Russian Foreign Minister Sergei Lavrov, wearing a USSR sweatshirt on his arrival in Alaska, said Moscow never revealed its hand in advance.
Ukraine and its European allies were heartened by a call on Wednesday in which they said Trump had agreed Ukraine must be involved in any talks about ceding land.
Zelenskiy said Trump had also supported the idea of security guarantees for Kyiv.
Russia, whose war economy is showing signs of strain, is vulnerable to additional US sanctions - and Trump has threatened tariffs on buyers of Russian crude, primarily China and India.
The day before the summit, Putin held out the prospect of something else he knows Trump wants - a new nuclear arms control agreement to replace the last surviving one, which is due to expire in February 2026.
Trump said on the eve of the summit that he thought Putin would do a deal on Ukraine, but he has blown hot and cold on the chances of a breakthrough.
Putin, meanwhile, praised what he called "sincere efforts" by the US to end the war.
The Russian leader has so far voiced stringent conditions for a full ceasefire, but one compromise could be a truce in the air war.
Putin has said he is open to a ceasefire but has repeatedly said the issues of verification need to be sorted out first.
Zelenskiy has accused Putin of playing for time to avoid US secondary sanctions and has ruled out formally handing Moscow any territory.
Trump has said land transfers could be a possible way of breaking the logjam.
Beyond territory, Ukraine has been clear in talks with Western allies that it needs a security guarantee backed by Washington.
Putin in 2024 stated his demands for stopping the war - the withdrawal of Ukrainian troops from the parts of Donetsk, Zaporizhzhia and Kherson regions that they still control, an area now of about 21,000 sq km.
Putin also said Kyiv would have to officially notify Moscow that it was abandoning its plans to join NATO, and it intended to remain neutral and non-aligned.
Ukraine says these terms are tantamount to asking it to capitulate.
