On his first day of duty, Secretary of State John Kerry vowed Monday to work to protect American service workers overseas from terrorist attacks during his first speech at the State Department.

He specifically mentioned Ambassador Chris Stevens and the three other Americans who lost their lives in the Sept. 11 attack on the U.S. Consulate in Benghazi, Libya.

"I will not let their patriotism and their bravery be obscured by politics, number one," he told his State Department colleagues Monday.

"Number two, 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 continued.

"We have tough decisions to make," Kerry said. "But I guarantee I'll do everything I can to live up to the high standards that Secretary Clinton and her team put in place."

Kerry also told State Department employees that he and President Obama were working to make America safer and the world more prosperous and peaceful.

Before his speech, Kerry spent much of Sunday reaching out to Palestinian and Israeli leaders. He assured them that the Obama administration is committed to pursuing peace in the Middle East.