 -- President Donald Trump officially declared the opioid epidemic a "national public health emergency" in an announcement at the White House Thursday.

The move diverges from previous promises -- even as recently as Wednesday night -- to declare the epidemic a "national emergency."

"Effective today my administration is officially declaring the opioid crisis a national public health emergency under federal law," the president said Thursday. "And why I am directing all executive agencies to use every appropriate emergency authority to fight the opioid crisis."

The president shared a personal story of his experience with addiction, through his brother Fred, who struggled with alcohol.

"I learned myself, I had a brother Fred, great guy, best-looking guy, best personality, much better than mine, but he had a problem. He had a problem with alcohol. And he would tell me, 'Don't drink. Don't drink,'" he said. "And to this day, I've never had a drink. And I have no longing for it. I have no interest in it."

He continued: "But it really helped me. I had somebody that guided me. And he had a very, very, very tough life because of alcohol, believe me, very, very tough life. He was a strong guy, but it was a tough, tough thing that he was going through. But I learned because of Fred, I learned."

Two senior administration officials confirmed to ABC News that the president will direct acting Secretary of Health and Human Services Eric Hargan to announce a nationwide public health emergency and also direct agency heads of other departments and agencies to exercise emergency authorities to minimize deaths and damage caused by the opioid crisis. USA Today first reported the details.

"A nationwide public health emergency will really reorient all of the federal government and executive branch's resources towards focusing on providing relief for this urgent need," an official said.

The Public Health Emergency Fund at HHS currently stands at $57,000, according to an agency spokesperson, and officials said the president's declaration won't yet include a request for Congress to replenish the fund.

House Minority Leader Nancy Pelosi, D-California, questioned the value of President Trump's opioid declaration today, calling on the White House to push for more funding to combat the epidemic.

"What I would say to the president on that is, "Show me the money,'" Pelosi said. "What is the point?"

"We all agree that this a place we have to go. I had the speaker write me a letter that we would continue to have the funding in the appropriations bill. But the president's statement are words without the money, and so we'd like to see [that]," she added.

The president had said as early as August he would be declaring a "national emergency," which many interpreted as his commitment to authorize a presidential emergency under the Stafford Act or the National Emergencies Act.

“The opioid crisis is an emergency, and I’m saying officially right now: It is an emergency. It's a national emergency,” Trump said at the time. “We’re going to draw it up and we’re going to make it a national emergency. It is a serious problem, the likes of which we have never had.”

The president teased the announcement on Wednesday, telling reporters an emergency declaration “gives us the power to do things that you can’t do right now,” but offered no additional details.

In an interview Wednesday night with Lou Dobbs on Fox Business Network, the president again alluded to the announcement he planned to make.

"There are a lot of good people that are seeing what's going on and I think we'll be successful in that next week I'm declaring an emergency -- a national emergency -- on drugs," Trump told Dobbs. "The opioid [crisis] is a tremendous emergency."

However, experts have told ABC News that declaring it an official national emergency, as Trump long touted he would eventually do, might have been a mistake.

Experts described the difference between the two potential declaration options before the president in interviews earlier this week.

The Stafford Act would have opened up federal resources such as FEMA's Disaster Relief Fund -- usually employed for natural disasters such as hurricanes Maria and Harvey.

This gives federal agencies the authority to cut red tape hindering recovery missions. Requests for funding from the Disaster Relief Fund come from a governor who claims the circumstances has overwhelmed his or her state's resources.

The president instead will ask the acting secretary of Health and Human Services to declare a public health emergency, which allows the agency to waive restrictions and deploy medical personnel to rural areas where medical options are limited.

The declaration follows a bombshell report from The Washington Post and CBS News’ "60 Minutes" implicating multiple members of Congress in the passage of a bill that significantly weakened the Drug Enforcement Agency’s enforcement capabilities in the opioid crisis in favor of lobbying by pharmaceutical companies.

Following the report, Rep. Tom Marino, R-Pa., withdrew his name from consideration to lead the Office of National Drug Control Policy.

The number of prescription opioids legally sold nearly quadrupled from 1999 to 2010, despite no change in the amount of pain that Americans reported, according to the U.S. Centers for Disease Control. Today, drug overdose is the leading cause of accidental death in the United States -- the majority of those lethal episodes involve an opioid.

"Every person who buys illicit drugs in America should know they are risking their future, their families, and even their lives," Trump said. "And every American should know that if they purchase illegal drugs, they are helping to finance some of the most violent, cruel, and ruthless organizations anywhere in the world."

The president made the crisis a primary talking point during his campaign for the White House and in March signed an executive order launching a commission led by New Jersey Gov. Chris Christie to explore ways to curb opioid abuse and overdoses.

On the campaign trail, he would often speak about the opioid crisis in states like New Hampshire and Ohio, but would often cite drugs pouring from across the U.S.-Mexico border as a primary driver of the problem.

He reiterated that specific concern with Dobbs on Wednesday and cited his planned wall along the U.S.-Mexico border as a deterrent.

"What's going on there [with] the drugs pouring into the country," Trump said. "I'll tell you what, we've made a big impact, but still, we need the wall. Part of the reason we need the wall is for drugs."

ABC News' Jeffrey Cook and Benjamin Siegel contributed to this report.