JOIN USHaqqani had met Zardari Sunday and spoke to him about the secret memo.
He then expressed his willingness to hand over his BlackBerry for investigation, reported Geo News.
Pakistani businessman Mansoor Ijaz alleged last month that a senior Pakistani diplomat asked for help in getting a message from Zardari to then chairman of the US Joint Chiefs of Staff, Admiral Mike Mullen.
Ijaz alleged that Zardari feared a military takeover following the US raid that killed Osama bin Laden in Pakistan May 2.
The businessman says he has phone records of calls allegedly from Haqqani and his US contact between May 9 and 10.
Prior to the memo issue, the Pakistan Army and the Inter-Services Intelligence (ISI) were upset with Haqqani over issuance of visas to Americans without "prior-scrutiny" by the Pakistani security agencies.
Before leaving Washington for Pakistan, Haqqani met US special representative to Pakistan and Afghanistan Marc Grossman.