The board of UBS
Citing an unnamed source, the SonntagsZeitung paper said the board would make the appointment on a telephone conference so Ermotti could present the bank's new strategy in New York as permanent CEO.
UBS declined to comment on the report.
Reuters reported last week that Ermotti, appointed interim CEO after Oswald Gruebel stepped down in the wake of a $2 billion rogue trading scandal, was close to clinching board backing as permanent CEO.
UBS Chairman Kaspar Villiger said on Tuesday the board does not want to hold up a decision on naming a permanent chief executive unnecessarily, but will not let itself be pressured into making a hasty decision either.
The board is seen as under pressure to end the power vacuum at the Swiss bank following the rogue trading incident.
Ermotti is expected to announce on Thursday UBS is scaling back its scandal-hit investment bank to focus on its core wealth management business but some analysts have suggested his interim position might have made a radical overhaul impossible.
(Reporting by Emma Thomasson; Editing by David Cowell)