Egypt has declined an invitation to a meeting of the Group of Eight industrialised nations in the US.
Mubarak apparently has a prior engagement
Egyptian Foreign Minister Ahmed Maher said President Hosni Mubarak had "other commitments".
The meeting is expected to discuss Washington's proposals for democratic reform in the Arab world, known as the Greater Middle East initiative.
The initiative, the US says, intends to counter Islamic militancy with political, social and economic change.
But it has been criticised by many Arab governments for seeking to impose reform from outside.
Some Arab governments have said the plan also fails to address key regional issues such as the Arab-Israeli conflict.
Mubarak proposals rejected
The Group of Eight is made up of the leading industrialised nations - Britain, Canada, France, Germany, Italy, Japan, Russia and the United States.
The summit is scheduled for 10 June in the southern US state of Georgia.
Cairo's refusal follows the close of an Arab League summit on Sunday which rejected Mr Mubarak's proposals for a unified Arab stance on the issue of reform.
Arab leaders also voted against creating a reform liaison and monitoring body in line with Washington's initiative.
The 22 Arab League members pledged to promote democracy, expand popular participation in politics and public affairs, reinforce women's rights and expand civil society.
The meeting was though marred by the non-attendance of several leaders and a walkout by Libya's Colonel Muammar Gaddafi.