US Secret Service chief to retire

Mark Sullivan is "retiring as of the 22nd of February," Secret Service spokesman Brian Leary told AFP, noting he had overseen 23 national security events, including the 2009 inauguration of President Barack Obama.

Sullivan, who took up his post in May 2006, saw the end of his term marked by a series of setbacks, most recently a prostitution scandal that erupted in April as agents helped prepare Obama's visit to a summit in the Colombian port city of Cartagena last year. Nine officers resigned or retired in the wake of the scandal.

Hundreds of Secret Service agents typically travel with, or before Obama when he goes overseas, in a huge security retinue.

April's incident was embarrassing to the Obama administration and led to allegations that national security or the president's safety might have been compromised.

Sullivan had to testify in Congress to assure that no security breaches were committed during the scandal. In its wake, the Secret Service announced it had toughened the rules regulating behavior of its agents abroad, including the consumption of alcohol and meetings with strangers.