"Our history is full of movements... We have to take a decision by tomorrow or the day after tomorrow," Dawn news reported citing Rehman as saying in his address to the participants of the sit-in on here on Saturday night.
The JUI-F supremo added that he would be evaluating options to "shift from this ground to a more effective ground".
"We don't want to worsen the situation. Fifteen million marches in nine months are enough for the evidence that how organised we have been and how (the participants of the marches) maintained the law and order situation."
Rehman also strongly criticised the incumbent government over its economic policy and declared the ruling regime a "security risk" for the country.
He said that the government in its first year borrowed more money than all the previous administrations collectively during the last 70 years.
He said that inflation increased during Khan's tenure of the incumbent government.
"Poor people in Pakistan are unable to purchase ration for their children," he said, adding that the country's economy under current government would further decline with each and every passing day.
The JUI-F chief said that writ of the incumbent government has ended and now "we will run the country".
"We will provide satisfaction and protection to the country," he said and asked the ruling regime to "step down" and don't test "our patience".
"We will remain in the arena until we get rid of the government."
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 the night of October 31.
Rehman has given Khan a two-day deadline to resign.
( With inputs from IANS )