By Marco Aquino

LIMA (Reuters) -Peruvian police handed over a convicted Dutch murderer to FBI agents on Thursday for transfer to the U.S., where he faces extortion and fraud charges related to the murder of an Alabama teenager two decades ago.

Joran Van der Sloot, a Dutch national from the Caribbean island of Aruba, has departed for the U.S. from a Peruvian Air Force base.

"This transfer will be temporary while the process in the United States lasts. Later, the Dutch citizen will be returned to Peru so that he can continue to serve his sentence in the Challapalca prison," Carlos Lopez, head of Interpol Lima, told reporters.

Television footage showed the Dutchman being escorted by armed police from a Lima prison where he has been serving a 28-year sentence for murder in a separate case. His extradition was approved in May by Peru's Council of Ministers.

Van der Sloot is set to face charges in the U.S. related to the mysterious disappearance and presumed murder of Natalee Holloway, an 18-year-old from a suburb of Birmingham, Alabama, who vanished during a high school graduation trip to Aruba in 2005.

He was previously arrested in the U.S. for her disappearance, but was not charged. Holloway's remains have never been found, though an Alabama judge declared her legally deceased in 2012, without settling the case. The young student was last seen in Aruba with Van der Sloot and another man.

Her disappearance prompted an exhaustive investigation and intense media attention.

Van der Sloot, 35, is accused of extortion and fraud for offering Holloway's family false information about the whereabouts of the teenager, according to U.S. authorities.

"The Peruvian authorities have signed a letter of guarantee, in which the American authorities agree to return this Dutch citizen (...) whether he is acquitted or sentenced," in a process that could take at least a year, Lopez added.

Van der Sloot was convicted in 2012 to 28 years in prison in Peru after he confessed to beating, strangling and suffocating a 21-year-old Peruvian business student in 2010.

(Reporting by Marco Aquino; Writing by Lucinda Elliott; Editing by Peter Graff, Jonathan Oatis and Marguerita Choy)