NEW YORK ( TheStreet) -- Sen. Tom Harkin (D., Iowa) announced Saturday that he won't seek re-election in 2014. In an announcement on his official Web site, the liberal Democrat cited his desire to spend more time with his wife and his age. "First, I'm going to fulfill a promise that I made to my wife Ruth, and that I also made to myself," Harkin said. "It's a promise that we're going to do certain things together -- and that we're going to live together in a way we've often talked about -- before it gets too late." The junior U.S. Senator from Iowa Harkin also said that at the end of his current Senate term -- his fifth -- he'll be 75. "When the current Congress is over, I will have served in the United States House of Representatives and the U.S. Senate for a total of 40 years," he said. "After 40 years, I just feel it's somebody else's turn." Harkin served in the House of Representatives from 1975 to 1985 before beginning his first Senate term in 1985.