The United Democratic Alliance MPs are currently voting for the party's preferred candidates for EALA slots.
The lawmakers are voting by secret ballot at State House to pick the five nominees for the East African Legislative Assembly.
The five will then be the UDA candidates in Parliament on Thursday when the MPs are expected to take a vote.
The party MPs are picking the five from the list of 15 who were shortlisted for the positions.
The president is said to have told the MPs that he does not want to dictate to them on who will represent the party.
The shortlist included Joel Nyambane, Geoffrey Karobia and Fred Muteti, Anne Too, Lilian Tomitom and Ziporah Kering.
Others are Yasser Bajaber, former Mombasa senator Hassan Omar, Jonas Kuko current EALA member Abdikadir Aden.
Ex-nominated senator Falhadha Iman and ex-Turkana Woman Representative aspirant Rebecca Lowoiya are also in the list of 15.