The first-term senator wrote a letter Sunday announcing his decision to state Democratic Party chairwoman Barbara Allen.
"I ... decided that I will not seek re-election to the United States Senate, in order to devote all of my energy to running for president," Edwards wrote.
Edwards won his first Senate term in 1998 but announced in January he would seek the presidential nomination.
North Carolina law allows Edwardsto run for president and Senate simultaneously.
State Democratic officials grew restless in recent months while Edwards considered whether to run for one or both.
Edwards' five-paragraph letter to Allen resolves that question and lets other Democratic candidates begin building their campaigns.
"It takes one question out of the way," said Scott Falmlen, executive director of the state Democratic Party. "We've said all along the best option .... was for John Edwards to be the presidential nominee" because it will energize party voters, he said.
"I'm sure there are people out there who have already made some end roads, but I've not heard from either of them," Allen said.
A timely decision became even more critical as U.S. Rep. Richard Burr, R-N.C., announced he would seek the GOP nomination for the Senate and began campaigning, while potential Democratic candidates cooled their heels in deference to Edwards.
With the White House's backing, Burr has raised $1.8 million this year for the Senate race and transferred another $1.7 million from his House campaign account, according to federal election reports.
Burr told WRAL Sunday night that: "I plan to stay focused on the things it will take for me to run a successful campaign, regardless of who my opponent will be."
According to Burr, no other candidates have expressed interest in the Republican nomination. But he added that: "Clearly, it's still early, and I expect other Republicans to show interest once we get closer to the filing period and other deadlines."
Burr also said he will be in Raleigh for a fundraiser at the Kerr Scott Building at the state fairgrounds on Sept. 12. He said he hopes Vice President Dick Cheney will be with him, but he could not confirm it because the White House will not confirm it more than 48 hours in advance.
Erskine Bowles, who lost to Sen. Elizabeth Dole in 2002 said he may enter the race. Former state House speaker Dan Blue had said he would consider a Senate run if Edwards declined.
Edwards' announcement eight months before the May party primary will give hopefuls the time to build their war chests, a political scientist said.
"I don't think he would want to inhibit the chances of the Democratic Party to field candidates," said Chalmers Brumbaugh with Elon University. "He's gotten a lot of criticism from goingthe two routes simultaneously. I just think he thought he couldn't be coy anymore about his intentions."
Edwards wrote that he and his family, on the campaign trail during the Labor Day weekend, took time "to discuss the next step in this journey."
"More than ever, regular North Carolinians and people all over the country need a voice in the White House representing them," his letter read. "The problems that drove me to explore a possiblecampaign are even more pressing today than they were in January.
"Given all of this, the decision to move forward decisively to seek the nomination was not a difficult one," he said.
Allen did not immediately return a phone call seeking comment Sunday night. An Edwards spokeswoman said the letter signifies that the exploratory phase of his campaign is over.
"He is ready and eager to move on to the next phase," Jennifer Palmieri said from Edwards campaign headquarters in Raleigh.
Bowles did not discuss his own plans in a statement Sunday night about Edwards' decision.
"I will support him in any way I can in this effort," Bowles said. "I applaud Senator Edwards for the courage of his decision and for his courage in the endeavor he has undertaken."
Blue said Sunday night there was no rush for him to announce his plans, and that he would talk to some people over the next couple of weeks "and look at some possibilities."
"I haven't been biting at John's heels," Blue said.
Republicans hold a slim majority in the Senate and could pad that lead based on the retirements of Democratic Sens. Ernest Hollings of South Carolina and Zell Miller of Georgia.
Edwards is set to formally announce his presidential candidacy Sept. 16 in Robbins, where he spent his high school years.
The senator has trailed in recent polls but received good news from a South Carolina survey released last week showing him neck-and-neck with three other candidates in the state where he wasborn.
Edwards has no plans to step down from his Senate seat before his term ends in January 2005, Palmieri said, even if he wins the party nomination.
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