U.S. Senator John McCain of Arizona, who was the Republican presidential nominee in 2008, said on Tuesday he will seek a sixth term in office in 2016.
McCain, the senior senator in the Republican-dominated southwestern state, formally announced his long-expected plans at an Arizona Chamber of Commerce & Industry event in Phoenix.
The 78-year-old McCain, who was first elected to the U.S. Senate in 1986, said he is ready to combat tough foreign and domestic challenges.
"No success in my life has ever come without a good fight, and there is so much worth fighting for today," he told an enthusiastic crowd. "I'm eager to get started and ready for whatever comes."
The Vietnam War veteran, who was held as a prisoner of war, has been a prominent voice on foreign policy issues. In 2008, he ran for the White House unsuccessfully against then-Democratic Senator Barack Obama.
McCain's bid for a sixth term comes after he took over as chairman of the powerful Senate Armed Services Committee in January.
The Republican senator has been known for his willingness at times to work across party lines.
Last year, at a meeting of the Arizona Republican Party a resolution passed by a voice vote censured McCain for what his critics called his overly liberal record, in a sign of continued distrust of him by some conservatives in the state.