WASHINGTON -- New Secretary of State John Kerry reported for duty Monday, acknowledging that as Hillary Rodham Clinton's successor he has "big heels to fill" and promising to protect U.S. foreign service workers from terrorist attacks overseas.

On his first day at the office in his new job, the former senator and 2004 Democratic presidential candidate was greeted with loud cheers by employees of the State Department and the U.S. Agency for International Development.

As the first man in the post in eight years, Kerry referred to his two most recent predecessors, Clinton and Condoleezza Rice, by asking in jest: "Can a man actually run the State Department?"

"I don't know," he answered. "As the saying goes, I have big heels to fill."

Kerry told his new agency's employees that he and President Barack Obama needed their help to make America safer and the world more prosperous and peaceful.

And after noting the deaths of Ambassador Chris Stevens and three other Americans in the Sept. 11, 2012, terrorist attack in Benghazi, Libya, Kerry said the protection of American diplomats would be a top priority.

"I guarantee you that beginning this morning when I report for duty upstairs, everything I do will be focused on the security and safety of our people," he said.

Kerry, 69, is the son of a diplomat and member of the Senate Foreign Relations Committee for 28 years – chairman since 2009. He spoke of his childhood time in Germany and learning the virtues of freedom.

As a 12-year-old in postwar Berlin of the 1950s, Kerry recounted how he could have caused a diplomatic incident by riding his bicycle around the destroyed and divided German capital, past the burnt out Reichstag and the Brandenburg gate and – using his first diplomatic passport – into the Soviet-controlled eastern part of the city.

"If the tabloids today knew I had done that, I can see the headlines that say, 'Kerry's Early Communist Connections!'" he joked, before describing more seriously how he explained to his irritated parents why he felt the need to cross the Iron Curtain.

"There were very few people. They were dressed in dark clothing. They kind of held their heads down. I noticed all this," Kerry said. "There was no joy in those streets. And when I came back, I felt this remarkable sense of relief and a great lesson about the virtue of freedom and the virtue of the principles and ideals that we live by and that drive us."

Kerry is likely to spend much of the week reaching out to foreign leaders. Over the weekend, he spoke to Israeli Prime Minister Benjamin Netanyahu and Palestinian President Mahmoud Abbas, as well as the foreign ministers of Japan, South Korea, Turkey, Canada and Mexico.

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  • John Kerry (2013-Present)

    John Kerry leaves a Senate Foreign Relations Committee markup on Jan. 29, 2013 after a vote was held on his confirmation as Secretary of State. (SAUL LOEB/AFP/Getty Images)

  • Hillary Clinton (2009-13)

    U.S. Secretary of State Hillary Clinton speaks at a press conference on November 14, 2012. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Condoleezza Rice (2005-09)

    Secretary of State Condoleezza Rice talks about the State Department's 2007 Country Reports on Human Rights Practices during a March 11, 2008 briefing in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Colin Powell (2001-05)

    U.S. Secretary of State Colin Powell speaks on June 22, 2004, about a corrected version of an inaccurate terrorism report issued by the government. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Madeleine Albright (1997-2001)

    U.S. Secretary of State Madeleine Albright delivers a Russia policy briefing on September 16, 1999 in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Warren Christopher (1993-97)

    U.S. Secretary of State Warren Christopher briefs reporters on the peace process in Bosnia during a Dec. 8, 1995 press conference. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Lawrence Eagleburger (1992-93)

    Then-acting Secretary of State Lawrence Eagleburger listens to a reporter's question during a Nov. 18, 1992 news conference at the State Department. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • James Baker (1989-92)

    James Baker III waves to his associates at the US State Department on August 13, 1992. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • George P. Shultz (1982-89)

    U.S. Secretary of State George Shultz listens to a question during his first day of testimony before Iran-Contra investigators on July 23, 1987 in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Alexander Haig (1981-82)

    Alexander Haig, Secretary of State-designate, a Reagan nominee on Monday, Dec. 23, 1980 in Washington for the announcement of selections. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Edmund Muskie (1980-81)

    (Pictured left) Freed hostage Richard Queen, right, greets well wishers at the State Department on Monday, July 21, 1980 in Washington. At left is Secretary of State Edmund Muskie. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Cyrus Vance (1977-80)

    Cyrus Vance, U.S. Secretary of State, pictured in 1979. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Henry Kissinger (1973-77)

    Secretary of State Henry Kissinger announces during an April 29, 1975 press conference in Washington that the evacuation of Americans from Vietnam and Saigon is complete, thus ending US involvement. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • William P. Rogers (1969-73)

    Israeli Defense Minister Moshe Dayan, left, and Secretary of State William P. Rogers begin talks at the Department of State on Feb. 7, 1972 in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Dean Rusk (1961-69)

    Secretary of State Dean Rusk is shown during a news conference in Washington, D.C., on March 1, 1962. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Christian Herter (1959-61)

    President Dwight Eisenhower, left, says goodbye to Secretary of State Christian Herter in Gettsburg, Pennsylvania, on May 2, 1959 as Herter is about to board a helicopter on the President's farm to return to Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • John Foster Dulles (1953-59)

    U.S. Secretary of State John Foster Dulles (left) gets together with South Korean President Syngman Rhee in Seoul on August 4, 1953. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Dean Acheson (1949-53)

    U.S. Secretary of State Dean Acheson speaks from the State Department on Nov. 29, 1950 in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • George C. Marshall (1947-49)

    Gen. George C. Marshall poses in his Red Cross office on Sept. 13, 1950 in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • James F. Byrnes (1945-47)

    James F. Byrnes, United States Secretary of State, links arms with Associated Press correspondent, John Hightower, at Central Hall, Westminster in London, Jan. 15, 1946. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Edward Reilly Stettinius (1944-45)

    France's Foreign Minister Georges Bidault makes a VE Day radio statement from the Opera House in San Francisco, CA, May 8, 1945. Seated at the far right U.S. Secretary of State Edward Stettinius. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>) <em><strong>Correction</strong>: An earlier version of this text misspelled Stettinius' surname.</em>

  • Cordell Hull (1933-44)

    U.S. President Franklin Roosevelt is greeted by Secretary of State Cordell Hull on Sept. 15, 1938 in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Henry Lewis Stimson (1929-33)

    Henry Lewis Stimson, American Secretary of State for War shown around July 1931. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Frank B. Kellogg (1925-29)

    Former United States Secretary of State Frank B. Kellogg on Aug. 17, 1936 at Waterloo Station in London. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Charles Evans Hughes (1921-25)

    (Center) Former Secretary of State and Chief justice Charles Evans Hughes, pictured on on March 27, 1931. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)