The timing of their trips has not been finalised but officials said the pair were most likely to come in November, when winter will be posing a new threat to millions of people left homeless by the October 8 disaster.
"There is a possibility that UN Secretary General Kofi Annan may visit Pakistan. The schedule has not been finalised," foreign office spokeswoman Tasnim Aslam told AFP.
"One possibility is that his visit may coincide with a donor's conference being held in Islamabad on November 18."
The spokeswoman added that Bill Clinton was planning to visit Pakistan, in the same way as he toured areas devastated by the December 2004 Indian Ocean tsunami.
"He has said he would visit Pakistan following the earthquake. When he would come, I can't say immediately as the dates are being firmed up," Aslam said.
A United Nations official speaking on condition of anonymity also said that Annan was set to visit Pakistan.
Annan has led calls for rich nations to contribute more to relief efforts after the 7.6-magnitude quake, which left more than 54,000 dead and 77,000 injured.
Clinton was recently enlisted by his successor President George W. Bush to help raise aid for communities in the southern United States that were devastated by hurricanes Katrina and Rita.