Updated

The new U.S. ambassador in Turkmenistan has presented his credentials to the president of this energy-rich former Soviet republic.

Robert Patterson takes up a post left vacated for five year, after a period of a chill in relations between the two countries.

The United States sees Turkmenistan as key to ensuring energy security in neighboring Afghanistan. Washington also backs initiatives to build transportation routes to carry the country's natural gas to Europe, thereby minimizing Western reliance on Russian exports.

Ties have come under strain, however, over Turkmenistan's interference in U.S. student exchange programs and embarrassing revelations made in cables leaked by the WikiLeaks website.