Eerik-Niiles Kross, who led IRL's campaign at the Tallinn local elections in October, said IRL should name the Estonian EU commissioner when Siim Kallas steps down in November.
Kross said a gentlemen's agreement had been struck with coalition partner Reform Party to that effect.
Speaking to Postimees on Saturday, Kross said the coalition agreed to promote Mart Laar to the post to succeed Kallas, who is the founder of the Reform Party. But Kallas's party might not extend that agreement to other IRL members, if Laar declines, preferring to move Andrus Ansip to Brussels instead.
Laar is unlikely to take the post, if it is offered, in connection with his taking the reins as supervsiory board chairman in the Bank of Estonia in April. His health could also play a role, as a stroke in February has left him in a wheelchair.
Kallas is one of five vice-presidents and is serving as Commissioner for Transport.
Speaking about the upcoming European Parliament elections, Kross said the Reform Party could tap foreign minister Urmas Paet as the next possible chairman of the party, asking him to lead the elections.
Estonia will go to the polls to elect its six MEPs, out of 751, at the end of May next year. Three out of the current six delegates are no longer members of the political parties they represented at the time they were elected.