North Dakota U.S. Sen. Kent Conrad said Tuesday he will not run for re-election in 2012, saying he will concentrate instead on reducing the national debt and dependence on foreign oil.

"It is more important I spend my time and energy trying to solve these problems than to be distracted by a campaign for re-election," the Democratic incumbent said in a statement sent to supporters. He currently chairs the Senate Budget Committee.

Conrad, 62, was elected to the Senate in 1986, when he was serving as state tax commissioner. His announcement followed last year's decision by North Dakota's other Democratic senator, Byron Dorgan, not to seek re-election. Dorgan was replaced by Republican John Hoeven, who had served as North Dakota's governor for the past decade.

Conrad, Dorgan and former U.S. Rep. Earl Pomeroy made up North Dakota's all-Democratic congressional delegation for 18 years. Pomeroy was defeated last November by Republican Rick Berg in a bid for his 10th term.

Conrad already had a prospective Republican challenger, state Public Service Commissioner Brian Kalk, who said last week he was forming an exploratory committee to test support for a Senate race.

Conrad said he would serve out his term.

"Although I will not seek re-election, my work is not done," Conrad said in his statement. "I will continue to do my level best for both North Dakota and the nation."

In Conrad's first campaign, he promised not to seek re-election unless the nation's budget and trade deficits had been brought under control.

He announced in 1992 that he was stepping down, saying his promise had not been fulfilled. But Conrad ended up running for the Senate that fall as a successor to North Dakota's other Democratic senator, Quentin Burdick, who died in September 1992.