Updated

The head of U.S. Customs and Border Protection has announced he is resigning, calling his relatively short tenure -- the product of a presidential recess appointment -- "one of the most rewarding experiences of my public life."

Alan Bersin, who had been the Obama administration's point man on border security issues, took the helm of nation's customs and border efforts in March last year after being among 15 officials installed by President Obama without Senate confirmation.

Thursday morning, Bersin notified Obama he would be leaving at the end of the month.

In a statement afterward, Bersin said it has been his "honor" to work with his CBP colleagues, and he is "immensely proud of the significant and meaningful achievements" they have made during his tenure.

"Through innovative solutions and strengthened partnerships, we have measurably strengthened border security, enhanced our ability to prevent potential terror threats, streamlined the entry process for lawful trade, and expanded our trusted traveler programs," Bersin said.

More than a year ago, Bersin said he "absolutely" planned to stay at CBP beyond what his recess appointment, which requires the Senate to approve his nomination to serve beyond the congressional term. Bersin said he had hoped to prove himself to skeptical members of Congress in the months ahead.

"Recess appointments have a history in all administrations, and I expect over time that people will come to see that it was a good choice, and I look forward to that. I look forward to earning that confidence with members of Congress," he told a group of reporters in April 2010, a month after becoming commissioner.

But the commissioner, who was first nominated to take the job in September 2009, was criticized by some in the Senate for failing to document the employment eligibility of those working in his home. As head of an agency responsible for protecting the borders, that remains an issue.

Now that he is leaving CBP, Bersin said he is departing with "full confidence that they will continue to secure our borders and foster the lawful exchange of people and goods with vigilance, service and integrity."

Before joining the Obama administration, Bersin served in a wide array of positions, including a stint as a private lawyer in Los Angeles, nearly five years as the U.S. attorney in Southern California, and more than a year as California's secretary of education under Governor Arnold Schwarzenegger.