US President Barack Obama has withdrawn the nomination of America's first ambassador to Somalia in 24 years, the White House announced.

The US Administration confirmed that Katherine Dhanani, a long-time diplomat with deep experience of African affairs, has turned down the nomination for personal reasons.

"She is withdrawing for personal reasons," an administration official said.

Dhanani had appeared before the Senate in March to seek confirmation in the post. President Obama nominated her for the post in February, the first since 1991.

Although the US never formally severed ties, the embassy in Mogadishu was closed in 1991 as Somalia descended into chaos amid a bloody power struggle among brutal clan chiefs.