The President cancelled his visit to Russia in view of the "evolving situation", state-run Radio Pakistan reported.
Zardari was due to leave for Russia tomorrow to attend the St Petersburg International Economic Forum and to hold bilateral talks with his Russian counterpart.
Zardari will play a crucial role in meetings to be held by the ruling Pakistan People's Party and its allies to choose a replacement for Gilani.
A three-judge bench headed by Chief Justice Iftikhar Chaudhry disqualified Gilani in response to several petitions that had challenged the National Assembly Speaker's decision not to disqualify the premier following his conviction of contempt.
The bench ruled that the post of premier had been vacant since April 26, when another seven-judge bench had convicted Gilani of contempt for refusing to reopen graft cases in Switzerland against Zardari.