Sheriff Rick Clark of Pickens County, S.C. is refusing to lower the flag outside of his office to half-staff to honor former South African President Nelson Mandela because the civil rights leader was not a United States citizen, the Associated Press reported.

President Barack Obama ordered flags lowered to half-staff for the South African international icon until sunset Monday. But Clark said he won't be lowering the flag in honor of Mandela in his department.

The AP reported that Clark first announced his decision on his Facebook page Friday, writing "Nelson Mandela did great things for his country and was a brave man but he was not an AMERICAN!!!"

He confirmed and reiterated his decision in several interviews on Friday.

"It's just my simple opinion that the flag should only be lowered to half-staff for Americans who sacrificed for their country," Clark told CNN affiliate WHNS.

He pointed out that Obama's order was a "proclamation and does not have the force of law," the AP reported.

Clark said he would have made the same decision if he was a sheriff in 2005 when President George W. Bush ordered flags flown at half-staff after the death of Pope John Paul II.

Clark became sheriff this year.

Clark told the AP that the sheriff's office American flag was at half-staff Friday to honor a Florence County deputy killed in a wreck and Saturday for Pearl Harbor Day, but will fly at full staff Sunday and Monday.

Mandela was imprisoned for nearly 30 years while trying to bring racial equality to South Africa. He later on became the country's president and a civil rights leader. He died Thursday.

Pickens County officials told the AP that Clark is free to do what he wants to do with the flag outside the sheriff's office, but American flags at other offices in the county will remain at half-staff to honor Mandela.