President Trump is expected this week to formally declare the opioid epidemic a national emergency, more than two months after verbally proclaiming it, which will help free up resources to respond to the crisis.

"The opioid crisis is an emergency," Trump said in August. "And I am saying officially right now: It is an emergency; it's a national emergency. We're going to spend a lot of time, a lot of effort, and a lot of money on the opioid crisis."

But filing the legal paperwork took time, requiring input from legal and and medical experts even as White House officials said that the process was under "expedited review." The paperwork details the kinds of responses the federal government and states will take and how long the emergency declaration will last.

Trump prepared reporters for the announcement as he took questions from the Rose Garden at the White House, reiterating that the work to prepare the declaration had been lengthy.

"We are going to be doing that next week," Trump said. "That is a very, very big statement. It's a very important step. And to get to that step, a lot of work has to be done and it's time-consuming work."

Declaring the epidemic a national emergency is unusual for a public health issue. Typically, a public health concern receives a "public health emergency" title from the secretary of Health and Human Services, such as the 2016 declaration for the Zika virus in Puerto Rico or the 2012 declaration in New York following Hurricane Sandy.

While such a declaration has been done before for a medical issue, such as former President Barack Obama's declaration on the swine flu epidemic, it is still considered unprecedented because it addresses issues of addiction, privacy, and potential distribution of treatment medications for widespread use.

The urgency for federal action has swelled as drug overdose deaths have become the largest cause of injury-related deaths in America. The latest available data on the U.S. opioid crisis, by the Centers for Disease Control and Prevention, show that in 2015 more than 33,000 people died of an opioid overdose, whether from prescription painkillers, heroin, or fentanyl. A CDC report published Thursday that dissected the data found that in recent years death rates from opioids in rural areas surpassed those of urban areas.

The national emergency declaration is in response to a recommendation by the Commission on Combatting Drug Addiction and the Opioid Crisis, which is overseen by Republican New Jersey Gov. Chris Christie and was created by Trump.

"Our citizens are dying. We must act boldly to stop it," the commission wrote in its interim report. "The first and most urgent recommendation of this commission is direct and completely within your control. Declare a national emergency."

Details of the declaration have not been released, but possibilities include providing over-the-counter naloxone, a drug that reverses an opioid overdose. It also could allow more doctors to prescribe drugs such as buprenorphine, which helps to subdue the withdrawal symptoms of someone with an opioid dependence. Some states that have declared emergencies have taken such steps.

Another possibility would involve waiving certain rules that would allow more treatment centers to be reimbursed by Medicaid. Under current rules for the program, a facility cannot receive funds if it has more than 16 beds.

The Trump administration has indicated that combatting the opioid crisis is a priority. Trump's Food and Drug Administration Commissioner Scott Gottlieb oversaw the agency's actions to have a powerful opioid taken off the market. Francis Collins, director of the National Institutes of Health, told the Washington Examiner in an interview in July that the Trump administration has allowed him to be particularly engaged in tackling the opioid crisis through developing new treatments for addiction and in researching alternative options to treat pain.

First lady Melania Trump also has been involved in the issue and has attended listening sessions with families affected by the crisis and with first responders, as well as a medical facility in West Virginia that cares for babies exposed to drugs during pregnancy.