Mohammad Hannon, Associated Press
In this Saturday, May 25, 2013 file photo, Republican Sen. John McCain speaks at a news conference at the World Economic Forum, held at the King Hussein Bin Talal Convention center, in Southern Shuneh, 34 miles (55 kilometers) southeast of Amman, Jordan. McCain announced Tuesday that he will run for re-election in 2016, making official a move that has been widely expected for the Republican as he looks to extend his nearly three-decade career in the Senate.

PHOENIX — Sen. John McCain announced Tuesday that he will run for re-election in 2016, making official a move that has been widely expected for the Republican as he looks to extend his nearly three-decade career in the Senate.

McCain described his plans to run before an Arizona Chamber of Commerce luncheon in Phoenix. He has signaled on several occasions in recent months that he was planning to seek a sixth term, but is now formally entering the race.

His appearance before a pro-business crowd comes ahead of a race in which he will likely face a challenge from the right amid tea party dissatisfaction over his record in the Senate. The Republican Party is currently divided between pro-business and conservative factions, and McCain's announcement location put him in friendly territory as he begins the race.

McCain will be 80 by Election Day, but says he is in great shape and has much work to do in the Senate.

"I work 16-hour days. Look at what I've done for Arizona and America," he told The Associated Press. "Make your own judgment."

McCain is a former prisoner of war during the Vietnam War who was first elected to the Senate in 1986, replacing longtime conservative stalwart Barry Goldwater. He ran for president in 2000 and secured the Republican Party's nomination in 2008, losing to Barack Obama. He coasted to re-election to the Senate in 2010.

McCain said he will emphasize local issues during his campaign, such as the drought, his work to benefit a copper mine and legislation to reform the Department of Veterans Affairs. The VA was thrown into turmoil last year amid allegations of misconduct and cover-ups at the VA hospital in Phoenix.

The most prominent Republican to hint of a possible challenge to McCain is state Sen. Kelli Ward, a conservative member of the Arizona Legislature. Whoever runs will be at a huge financial disadvantage against McCain, who already has more than $3.5 million in cash on hand.

"We certainly anticipate a challenge both from right and left, and we'll be ready," McCain said.

Glenn Hamer, president of the Arizona Chamber of Commerce and industry, said McCain never takes anything for granted in a political race and has a deep reservoir of support in Arizona. That combined with his national security credentials should easily overcome any primary challenge in 2016, Hamer said.

"I would expect that he would be overwhelmingly re-elected," he said.

McCain was elevated to chairman of the Senate Armed Services Committee this year after his party reclaimed the Senate. He has repeatedly used his stature on the committee to attack Obama's foreign policy decisions.