He demanded that Khan's 'selected' government must step down, paving the way for fresh elections.
"We will keep changing our strategy till the 'selected government' (not chosen by the people, but by the army) of Khan steps down," he said talking to foreign journalists.
According to some media reports, the JUI-F members have been asked to join the movement with enough eatables and other necessary things, which signals that the movement may last long.
The JUI-F Azadi March is scheduled to begin on October 27 from different cities across Pakistan and enter Islamabad on October 31.
"We are sure of entering Islamabad with as many as one million protesters. If we reach Islamabad, our action plan will be different. But if not allowed, the march will turn into 'fill the jail' movement," said Rehman.
The JUI-F chief said his party's movement against the government would be within the constitutional limits.
"We don't wish to clash with any of the institutions. We are in touch with all relevant institutions and people from all walks of life to make our protest a success. In the last one year, unemployment has increased manifold due to poor economic policies, causing disappointment among people. The Khan-led government has failed on every front." he said.
( With inputs from IANS )