Democratic U.S. Senator Tom Harkin of Iowa said Saturday he will not seek a sixth term in 2014.

Harkin announced his decision during an interview with The Associated Press, and said the move could surprise some.

The 73-year-old Harkin cited his age — he would be 81 at the end of a sixth term — as a factor in the decision, saying it was time to pass the torch he has held for nearly 30 years.

Harkin, first elected in 1984, ranks 7th in seniority, and 4th among majority Democrats. He is chairman of the health, education, labor and pensions committee, and chairman of the largest appropriations subcommittee.

He has long aligned with the Senate's more liberal members, and his signature legislative accomplishment is the 1990 Americans with Disabilities Act. He also served as a key salesman of President Barack Obama's 2010 health care bill.

Although members of his family have been diagnosed with cancer, Harkin said his health is good —But he said "you never know," and that he wanted to travel and spend his retirement with his wife Ruth "before it's too late."

The news creates a rare opening for an Iowa Senate seat. Harkin is Iowa's junior senator, outranked by Republican Charles Grassley, who has held the state's other seat since 1980.

Democrats hold a 55-45 advantage in the Senate, requiring Republicans to gain six seats to win back the chamber. But Democrats have more seats to defend in 2014_20 compared to only 13 for Republicans.

And the president's party historically loses seats in the midterm elections after his re-election.

From Associated Press