Ababu Namwamba has stepped down as the Foreign Affairs Chief Administrative Secretary.
"I thank the president for the appointment, but it is time to vacate the seat," he said.
Speaking to the media, Ababu applauded the team that runs the ministry affairs department.
"We have accomplished so much and during this four-year period, we have had an amazing time," he said.
The former Budalangi MP will take up his new role as Deputy President William Ruto's roving envoy on international relations.
Ababu thanked Ruto for the appointment to his secretariat.
"I am thankful for the confidence they have demonstrated by inviting me to play that critical role. I believe that I will bring a wealth of experience to this new post," he said.
"I will deploy all these credentials in driving our foreign policy and segments for the campaign. I want to assure our friends and partners that I will be available to define our policy as a campaign team preparing to form the next government," he said.
Ruto on Wednesday appointed Ababu to the post at his Presidential campaign secretariat.
Under his new role, the CAS will be responsible for Ruto's internal image and relations ahead of the August 9 General Election.