NASA principals will "unveil the team that will redeem Kenya" at Uhuru Park in Nairobi on April 27.
It is expected that they will name the principal who will challenge President Uhuru Kenyatta on August 8.
"We have a date with you," Ford Kenya leader Moses Wetang'ula told a charged meeting at Bomas of Kenya.
Wetang'ula said the decision will not affect the principals positions as equals.
"I assure Kenyans that we bound ourselves in the name of God that none of us will think twice or walk out of this arrangement."
Other members of the coalition are Raila Odinga (ODM), Musalia Mudavadi (Amani), Kalonzo Musyoka (Wiper) and Isaac Rutto (CCM).
Rutto of Chama Cha Mashinani joined the team on Tuesday.
The principals have been under pressure to name the person who will battle it out with President Uhuru Kenyatta on August 8.
They dismissed claims of infighting and a split, and said they will take their time to name the coalition's presidential candidate.
On Wednesday, Machakos Senator Johnson Muthama said: "We have a flag bearer and very soon Kenyans will get to know where we are heading. We meet tomorrow at Bomas...you will hear a lot from us."
Muthama told the media in Nairobi that they cannot let Kenyans down by failing to name the flag bearer on time.
He was with Siaya Senator James Orengo, chair of the 12-member steering committee working on the National Super Alliance plan.
Thank you for participating in discussions on The Star, Kenya. Note that:
- Unwarranted personal abuse and defamatory statements will be deleted.
- Strong personal criticism is acceptable if justified by facts and arguments.
- Deviation from points of discussion may lead to deletion of comments.