Mama Rachel Ruto made the promise after sharing the spotlight with former PM Raila Odinga's wife, Ida.
In a post on Twitter, Mama Rachel congratulated Mrs Kenyatta on the relaunch of the First Lady's Half Marathon albeit in a new name.
Mrs Ruto assured the First Lady that she would be available to join the marathon on March 10, 2019 when the Beyond Zero Marathon will take place for the first time.
"We are all very proud of Our First Lady! It was such an honor to join her in the launch of Beyond Zero Marathon that will be held next year on the 10th of March.
"We applaud you our First Lady! We shall be there to run with you," her tweet read.
Mama Ida Odinga
Mrs Kenyatta launched the Beyond Zero Marathon on Tuesday alongside Rachel and former Prime Minister Raila Odinga's wife Ida.
The First Lady issued the two female national figures with t-shirts ahead of the 2019 race with hopes to raise enough money to fund the Beyond Zero campaign.
The First Lady's Half Marathon took a hiatus in 2017 to allow the political campaigns season to pass.
The First Lady however assured Kenyans that the cause remains until the betterment of maternal healthcare in the country, and to build the Beyond Zero Referral Hospital was achieved.
“I remain committed to and will not deviate from my ultimate goal, which is the betterment of maternal healthcare in this country, and, to build the Beyond Zero Referral Hospital," the First Lady stated.