Opposition leader Raila Odinga has sent Siaya Senator James Orengo to the Nasa summit in Athi River.
The meeting was called by Nasa principals Kalonzo Musyoka, Musalia Mudavadi and Moses Wetang’ula to discuss Raila's Friday deal with President Uhuru Kenyatta.
The Opposition leaders are expected to deliberate on the future of the coalition following the latest developments.
However, Raila's spokesman Dennis Onyango told the Star that the ODM leader was likely to attend.
After their talks at Harambee House, Raila and Uhuru agreed to unite for peace and healing after last years' bruising political battle.
In a statement that followed the talks, Nasa leaders said they will discuss the development at a retreat.
"While we have always advocated for dialogue as co-principals of the Nasa coalition, we were not privy to the discussions at Harambee House," they said in their statement last week.