Mr Mwanawasa chairs the Southern African Development Community
Zambian President Levy Mwanawasa has been flown to the French capital, Paris, for specialist medical treatment after suffering a stroke in Egypt.
The president, 59, was rushed to hospital on Sunday ahead of the African Union summit in Sharm el-Sheikh.
Vice-President Rupiah Banda said his condition "remains stable".
The AU summit called for a unity government in Zimbabwe. Mr Mwanawasa had taken a tough line against President Robert Mugabe's regime.
As chairman of the Southern African Development Community (Sadc) he had said he sympathised with Zimbabwean opposition leader Morgan Tsvangirai when he withdrew from the presidential election because of political violence against his supporters.
"Elections held in such an environment will... bring embarrassment to the Sadc region and the entire continent of Africa," he said then.
He has compared the economic situation in Zimbabwe to "a sinking Titanic".