LAS VEGAS — U.S. Rep. Jim Clyburn of South Carolina endorsed Hillary Clinton in the Democratic presidential primary on Friday, one week before voters in the state go to the polls and a day before Nevada Democrats caucus in a closer-than-expected race with Vermont Sen. Bernie Sanders.

Clyburn said that he chose to break his pledge of neutrality under pressure from family and friends, including some who thought the endorsement might boost Clinton on the eve of the Nevada caucuses, which will be held on Saturday.

"A few days ago, I admitted that my head and my heart were in different places relative to this year’s presidential primary," Clyburn said. "Today, however, my head and my heart were in the same place."

"My heart has always been with Hillary Clinton, but my head had me in a neutral corner."

Clyburn, a longtime South Carolina lawmaker, is considered the most coveted endorsement in the state. He said Friday that he sought to keep the state competitive by not endorsing any candidate in the primary, a philosophy he maintained in the 2008 contest between Clinton and Barack Obama.

"I believe that the future of the Democratic Party and the United States of America will be best served with the experience and know-how of Hillary Clinton as our 45th president," Clyburn said. 

In 2008, Clyburn endorsed Obama after the South Carolina vote. The contentious primary that year left lingering bad blood with the Clintons. Clyburn recalled that former president Bill Clinton had called him at 2 a.m. to express his displeasure.

"He was very upset, his wife had just suffered a major defeat in the South Carolina primary and I had not been involved in it, but Bill Clinton thought otherwise," Clyburn said. "He had a right to feel that way."

Asked on Friday about his relationship with the former president, Clyburn said that the rift had been repaired.

"I hold no ill will at all about Bill Clinton being active on behalf of his wife," Clyburn said. "That’s as it should be."

Asked about the Nevada caucuses, which have become hotly competitive, Clyburn said that the closeness of that race played into his decision-making process.

"I was on the phone with a few of my friends in Nevada... some of whom urged me to come forward now expressing that it may help them in Nevada," he said. "I certainly hope so."

The 24-year lawmaker is also a veteran of the civil rights movement who counts as his friends some prominent Clinton endorsers, including Rep. John Lewis of Georgia.

Clyburn recalled his experiences in the civil rights era and his arrest for fighting segregation and for the right to vote when asked about why so many young voters are not supporting his chosen candidate, Clinton.

"I say to young people, get involved," Clyburn said. "Whoever you are for, you go out you work [for] that candidate and you vote."

"Vote. Get involved. Wherever your passions take you, go there," Clyburn added. "I don’t have any problem  with anybody who’s out working for Bernie Sanders."