Papua New Guinea's former Treasurer Patrick Pruaitch has been nominated as the opposition's choice for prime minister in a motion of no confidence against Peter O'Neill.
Parliament resumes this afternoon and the opposition is expected to lodge a motion which, if in order, could result in a confidence vote against Mr O'Neill next week.
The prime minister has been under growing pressure to resign and two days ago announced he would step down in the coming days.
However he subsequently filed a Supreme Court application regarding the rules of motions of no confidence, with his office confirming he would delay stepping down.
The opposition has been bolstered by mass defections from Mr O'Neill's coalition government over recent weeks.
The prime minister has selected PNG's former leader, Sir Julius Chan, to replace him.
However Sir Julius has objected to Mr O'Neill's court action and urged a prompt transition of power.