Rehman, head of the Jamiat Ulema-e-Islam-Fazl party, made the statement after he and four party members returned from a visit to Kabul, Dawn News reported Monday.
A statement issued by Karzai's office said the president and Rehman both called for cooperation against terrorism.
Rehman declined to reveal any further details about the meeting.
The delegation also met with members of the Afghan High Peace Council, where they discussed the role of the cleric's party and other religious leaders in relation to the situation in Afghanistan.
Rehman supports the Taliban's fight against foreign troops in Afghanistan, but the Afghan Taliban said in a statement the visit was "a deliberate ploy to weaken the Taliban."