The National Super Alliance has changed the venue for swearing in Mr Raila Odinga and Mr Kalonzo Musyoka as People's Assembly president and deputy.
This comes even as US ambassador to Kenya Robert Godec held a meeting with Mr Odinga yesterday at Capitol Hill, the latter's private office, to convince him abandon the plan.
Mr Odinga's secretary Dennis Onyango did not give details of the meeting.
Mr Godec has been calling for dialogue and has since held separate meetings with Nasa principals and its leadership in the National Assembly as well as those from the ruling Jubilee party side.
The ambassador wants the two opposing sides to engage in a dialogue that would hopefully end the political stalemate.
Nasa has given President Uhuru Kenyatta until January 30 to initiate the talks failure to which Mr Odinga would be sworn in.
Among the demands that the opposition has put on table include changes to the electoral regime and changing the system of governance from pure presidential to parliamentary.
President Kenyatta maintains he will only take part in such negotiations if they are about development.
A Nasa MP told the Nation yesterday that the swearing-in ceremony would not be held at Uhuru Park as earlier announced.
"When we chose Uhuru Park, we knew the Jubilee leadership would thwart our mission by ensuring the venue is cordoned off by police. We have chosen a different location that will be known during or after the event," the lawmaker, who did not want to be named, said.
The city county government says a church and a group called Nairobi Business Community have applied to use the grounds on January 30, the date for Mr Odinga's swearing-in ceremony.
Nasa co-principal Musalia Mudavadi yesterday said preparations for the ceremony were on and that nothing would stop Nasa from achieving what it promised Kenyans.
"Our communication in Mombasa on Sunday was clear. As long as there is no contrary message, the swearing in is on," Mr Mudavadi said.
Mr Musyoka is on record telling Jubilee bosses "to stop their belligerence".
"I'm for dialogue because I don't want Kenya to go the South Sudan or Somalia way. We want peace and it starts with Mr Kenyatta," he said.