The leaders and office-bearers of the two parties said on Friday that they had already told Rehman in categorical terms that they would only attend the public meeting and would not support any sit-in, Dawn news reported.
The parties said they had not issued any specific directives to their workers and activists regarding participation in the sit-in.
"We came only for one day," PML-N Secretary General Ahsan Iqbal told Dawn news on Friday.
Iqbal, who also addressed the Azadi march participants with PML-N president Shahbaz Sharif, said that even party's supreme leader Nawaz Sharif had asked them to participate in the Azadi March for one day only.
Similarly, PPP Secretary General Farhatullah Khan Babar said his party leadership had made it clear that it would not take part in an "indefinite dharna (sit-in)".
When asked about the possibility of PPP's participation in the sit-in if it was extended beyond Sunday, he said he could not make a comment without discussing the matter in the party.
The 'Azadi March', which was spearheaded by the JUI-F to call for toppling the incumbent Pakistan Tehreek-e-Insaf (PTI) government, entered Islamabad on Thursday night.
Rehman has given Prime Minister Imran Khan a two-day deadline to resign.
( With inputs from IANS )