By Jan Wolfe

WASHINGTON (Reuters) - U.S. President Donald Trump on Thursday said he may declare the coronavirus pandemic an emergency by invoking a law known as the Stafford Act.

The following explains how the Stafford Act works and what powers a declaration would unlock.

WHAT IS THE STAFFORD ACT?

The law, enacted in 1988, empowers the Federal Emergency Management Agency (FEMA) to assist state and local governments during "natural catastrophes" and coordinate the nation's response.

FEMA, an agency within the U.S. Department of Homeland Security, controls more than $40 billion in federal funding set aside by Congress for disaster relief. FEMA could use that funding to help build medical facilities and transport patients, among other measures.

Only the president can declare a major disaster under the law.

"We have very strong emergency powers under the Stafford Act," Trump told reporters in the Oval Office on Thursday. "I have it memorized, practically, as to the powers in that act. And if I need to do something, I'll do it. I have the right to do a lot of things that people don't even know about."

Trump has invoked the Stafford Act many times during his presidency, approving major disaster declarations to address flooding in the Midwest and wildfires in California, among other events.

FEMA is commonly associated with natural disaster response but the agency can also address pandemics.

In 2000, former President Bill Clinton used a Stafford Act emergency declaration to pay for mosquito control efforts to address outbreaks of the West Nile virus in New Jersey and New York.

DIDN'T THE U.S. ALREADY DECLARE CORONAVIRUS AN EMERGENCY?

A different government agency, the U.S. Department of Health and Human Services, declared the coronavirus a public health emergency in late January and has been the lead agency addressing the pandemic.

HHS's declaration, made under a different law than the Stafford Act, allowed U.S. officials to impose restriction on individuals entering the country from China, among other measures.

Several state governments have declared emergencies, allowing them to mandate containment zones like the one in New Rochelle, New York and address price-gouging.

Cartoons on the Coronavirus View All 383 Images

WHAT OTHER LAWS COULD TRUMP INVOKE?

Last year Trump declared an emergency on the southern border to circumvent Congress and take money already designated for other programs to pay for his U.S.-Mexico border wall, which he promised to build during his 2016 campaign.

That declaration was made under the National Emergencies Act of 1976, not the Stafford Act. The law does not define "emergency,” giving the president broad discretion to declare one.

An emergency declaration under the National Emergencies Act unlocks sweeping presidential powers, like the ability to seize control of the internet or suspend laws, while a Stafford Act declaration deals only with FEMA.

In 2009, former President Barack Obama declared the H1N1 influenza, or "swine flu," pandemic to be a national emergency under that law.

Obama's declaration waived some federal health insurance rules to speed treatment.

(Reporting by Jan Wolfe; Editing by Noeleen Walder and Lisa Shumaker)