U.S. Secretary of State John Kerry (L-R) takes his seat with Tanzania's President Jakaya Kikwete and Ghana's President John Dramani Mahama as they arrive for a civil society forum during the U.S.-Africa Leaders Summit in Washington. REUTERS/Jonathan Ernst

Khartoum - The attendance of nearly every African nation at an unprecedented summit in Washington on Monday is “abnormal” as long as Sudan is excluded, Khartoum says.

Sudan's President Omar al-Bashir, who is wanted for alleged war crimes, is one of only four leaders not invited by US President Barack Obama for the three-day meeting focussed on building economic ties between the two continents.

“It was abnormal that Africa accepts to go to this meeting while one of its very important members was not invited,” Sudan's Foreign Minister Ali Karti said in comments published Monday by Sudanese newspapers.

Islamist-run Khartoum has been under US economic sanctions since 1997 over what Washington said were human rights violations and other issues.

In 2009 and 2010 the International Criminal Court in The Hague issued arrest warrants for Bashir for war crimes, crimes against humanity and genocide allegedly carried out in Sudan's Darfur region.

Fifty African heads of state were sent invitations to the summit, the greatest ever concentration of African leadership in Washington.

Zimbabwe's Robert Mugabe, Eritrea's Issaias Afeworki and the Central African Republic's transitional leader Catherine Samba Panza were also left off the guest list.