The SLPP has asked president Ranil Wickremesinghe to obtain the support of up to 25 SJB MPs as promised without any further delay.
Supporters of the president have refused to ally with the government as long as the Rajapaksas remain as its partners.
If the SLPP comes in the way of the government obtaining support from SJB MPs, it is prepared even to leave the government, a SLPP spokesman said.