The well connected Jonathan Noble of Autosport reported Wednesday that the final negotiations between Lotus and Caterham ended on a positive note.
Kovalainen was still under contract with Caterham, and drove the Renault-powered car during some Friday free practice sessions earlier this year. As of Thursday, Kovalainen will be released from Caterham to race for Lotus in the United States and Brazil.
Lotus is expected to make an announcement confirming Kovalainen's deal on Thursday morning, just hours before he is due to arrive at Circuit of the Americas near Austin.
Kovalainen's deal comes after efforts to sign Sauber’s Nico Hulkenberg came to nothing when the German decided against joining the team, despite having visited Enstone earlier this week.