WASHINGTON (Reuters) - International Monetary Fund Managing Director Kristalina Georgieva on Tuesday nominated former IMF official Antoinette Sayeh to become the organization's No. 2 official, passing over a U.S. Treasury official who had been viewed as a top candidate.

Sayeh, a Liberian national, was director of the IMF's African Department between 2008 and 2016. She since has been at the Center for Global Development think tank in Washington, and previously served as Liberia's finance minister and spent 17 years at the World Bank.

Georgieva's move to appoint her, which is subject to approval by the IMF board, comes after Geoffrey Okamoto, a 35-year-old U.S. Treasury acting assistant secretary had emerged as a leading candidate, backed by U.S. Treasury Secretary Steven Mnuchin.

Sayeh, 61, would replace economist David Lipton, who will leave the IMF at the end of February after serving nearly nine years as the Fund's first deputy managing director, a role that has a strong influence over the organization's policies.

If confirmed, her appointment would break a long-standing tradition of Americans serving in the No. 2 position, as the IMF managing director has been traditionally a European. The United States is the largest shareholder in the IMF, with 16.5% of the Fund's voting power.

"Antoinette demonstrates a rare combination of institutional leadership, deep analytical capacity, and an unwavering commitment to fairness," Georgieva said in a statement.