WASHINGTON (Reuters) - The workforce at the U.S. Environmental Protection Agency is on course to fall to its lowest level since Ronald Reagan was president, an agency official said on Tuesday.

Environmental Protection Agency (EPA) workers and supporters protest job cuts during rally in Chicago, Illinois, March 2, 2017. REUTERS/John Gress

In June, the EPA unveiled a buyout program that would contribute to the biggest cuts of any federal agency in President Donald Trump’s 2018 budget proposal. The EPA employs about 15,000 people.

After buyouts and retirements, that number could drop to 14,428 by October, the official, who spoke on condition of anonymity, said in an email.

That would be below the fiscal 1988 level, when EPA staffing was 14,440, the official noted. A further 2,998 employees, or just over 20 percent of the total, are eligible to retire now, the official said.

The Trump Effect See how Reuters is tracking President Donald J. Trump’s impact on energy and the environment, healthcare, immigration, and business and the economy

In an April spending bill, the Republican-controlled Congress set a cap for EPA staffing at 15,000 employees for fiscal year 2017, rejecting proposed increases by the previous administration of Democratic President Barack Obama.

EPA Administrator Scott Pruitt said the reductions were “giving long-serving, hard-working employees the opportunity to retire early.

“We’re proud to report that we’re reducing the size of government, protecting taxpayer dollars and staying true to our core mission of protecting the environment and American jobs,” he said in a separate statement.

Pruitt has rolled back a slew of Obama-era regulations limiting carbon dioxide emissions from fossil fuels.

He was also instrumental in convincing Trump to withdraw the United States from the Paris climate accord - a global pact to stem planetary warming through emissions cuts.

While acknowledging the planet is warming, Pruitt has questioned the gravity of the problem and the need for regulations that require companies to take costly measures to reduce their carbon footprint.

Before becoming head of the EPA, he was Oklahoma’s attorney general and repeatedly sued the agency he now runs to block federal environmental rules.