United States ambassador to Kenya Scott Gration has resigned citing differences with Washington over his leadership style, just a year into his appointment.

The resignation is seen as a big diplomatic blow which is likely to make public the relations between Washington and its envoys abroad, especially as the US pushes for a larger influence in key regions such as Africa.

In his statement, Gration said he had differences with US administration, without giving further details.

“Differences with Washington regarding my leadership style and certain priorities lead me to believe that it’s now time to leave,” said Gration in statement sent to the press.

Gration was appointed on May 2011 having served as a special envoy to Sudan in 2009. He leaves his post on July 28 having submitted his resignation notice to US President Barack Obama and Secretary of State Hillary Clinton to inform them of his decision last Monday.

President Obama picked Major General (rtd) Gration to replace Michael Ranneberger last year.

The US unveiled a strategy paper two weeks ago describing Africa as "the next major economic success story," underscoring the increased attention that Africa has been getting as the land of opportunity in the wake of financial and economic crises that have hit North America and Europe hard, and as the booming BRIC economies -- Brazil, India, China and Russia -- begin to slow down.

The White House brief indicates that the US will partner with sub-Saharan African countries to pursue four major objectives -- strengthen democratic institutions, spur economic growth, trade and investment, advance peace and security and promote opportunity and development.

The new strategy indicates that the US intends to build on its Africa trade-focused programmes such as the Partnership for Growth and New Alliance for Food Security and Nutrition, as well as international programmes such as the Open Government Partnership and the Extractive Industries Transparency Initiative, to "encourage legal, regulatory, and institutional reforms that contribute to an environment that enables greater trade and investment in sub-Saharan Africa."

The brief says that the US will work with Congress to extend the unilateral preferences under Africa Growth and Opportunity Act (Agoa) beyond 2015 and extend the Generalised System of Preferences beyond 2013, while also exploring ways to update these programmes and enhance African capacity to fully utilise and benefit from them.