US Senator Carl Levin, a six-term Democrat and fierce advocate for military personnel and readiness, announced Thursday he will not seek re-election in 2014.

The chairman of the powerful Senate Armed Services Committee said he would rather spend his final two years as a lawmaker unencumbered by "the distraction of campaigning for re-election."

"I have decided not to run for re-election in 2014," the 78-year-old Levin, first elected to the Senate in 1978, said in a statement.

"This decision was extremely difficult because I love representing the people of Michigan in the US Senate and fighting for the things that I believe are important to them."

Levin is the sixth senator this year -- and the fourth Democrat -- to announce he is not seeking re-election in 2014, setting up yet another likely fierce battle for his vacated seat next year.

Three of the Senate's longest-serving Democrats, Tom Harkin, Jay Rockefeller and Frank Lautenberg, have announced they won't be running again, while Republicans Saxby Chambliss and Mike Johanns have done the same.

Levin said he wanted to focus his remaining two years in the chamber on issues like campaign finance reform and cracking down on corporate tax avoidance schemes that lead to massive revenue losses at the US Treasury.

"These schemes add hundreds of billions of dollars to the deficit... and they add to the tax burden of ordinary Americans who have to pick up the slack and accelerate the economic inequality in our country," he said.

His older brother Sandy Levin represents Michigan in the US House of Representatives.