President Trump quietly signed a long-anticipated executive order on Tuesday intended to force low-income recipients of food assistance, Medicaid and low-income housing subsidies to join the work force or face the loss of their benefits.

The order, in the works since last year, has an ambitious title — “Reducing Poverty in America” — and is directed at “any program that provides means-tested assistance or other assistance that provides benefits to people, households or families that have low incomes,” according to the order’s text.

But its programmatic goals are considerably more modest, officials said. Many of the initiatives outlined have already been set into motion by the affected agencies, particularly the Department of Health and Human Services, which has begun issuing waivers to Republican governors who want to impose stricter work requirements on Medicaid recipients as a way to reduce costs.

And advocates for poor people questioned whether the order could achieve even modest goals, saying most able-bodied adults who receive noncash federal aid either already work or face significant impediments to doing so.

The order gave all cabinet departments 90 days to produce plans that impose work requirements on able-bodied aid recipients and block ineligible immigrants from receiving aid, while drafting “a list of recommended regulatory and policy changes” to push recipients off the rolls and into jobs.

“President Trump has directed his administration to study policies that are failing Americans,” said Andrew Bremberg, the president’s domestic policy chief, who briefed reporters on the order’s contents in a telephone call late Tuesday. Journalists were not provided with copies of the document beforehand.

The aim, Trump aides said on the call, is to prod federal and state officials to take a tougher stance with aid recipients — millions of whom currently receive exemptions from existing work requirements because they are in training programs, provide care for relatives or volunteer their labor.

The Agriculture Department is already pressuring states to impose work requirements in the Supplemental Nutrition Assistance Program, the program formerly known as food stamps. Earlier this year, the Department of Health and Human Services granted a waiver to Arkansas so it could require Medicaid recipients to get jobs, participate in job training or engage in job searches at least 80 hours a month.

Advocates say most able-bodied adults who do not already have jobs face obstacles including mental problems, criminal records that deter employers from hiring them and complicated family situations.

A 2017 study of Michigan’s Medicaid program by the University of Michigan Institute for Healthcare Policy and Innovation found that three-quarters of those enrolled in the program were already working or physically unable to do so. Another 12 percent were people likely to be exempt, including the elderly and students.

“It’s a little bit of a solution in search of a problem,” said Elaine Waxman, a senior fellow with the nonpartisan Urban Institute, who has studied food assistance programs and other government entitlements. “The administration is reflecting a larger narrative that many low-income individuals avoid work — but there’s just not a lot of data to support that position. Many of these people have significant barriers to working full time.”

But the greater significance of the order might be semantic — and political.

The order — signed in private on a frenzied news day dominated by congressional testimony from Mark Zuckerberg, the Facebook chief executive, a potential military response in Syria and the president’s rage at the raid on Monday on his personal lawyer’s office — tries to redefine “welfare” to fit the catchall term Mr. Trump used in campaign speeches.

The word “welfare” — politically loaded and often pejorative, especially among the president’s conservative supporters — has historically been used to describe cash assistance programs such as Temporary Assistance for Needy Families.

The Trump administration wants to change the lexicon. On Tuesday, Mr. Bremberg sought to stretch the term to encompass food aid and Medicaid — programs even many conservative lawmakers view as a necessary safety net for families and individuals on the economic margins through no fault of their own.

“Our country suffers from nearly record high welfare enrollments,” Mr. Bremberg said. But Temporary Assistance for Needy Families payments to poor people are approaching record lows.

Mr. Trump, several aides said, is unconcerned — or perhaps even unaware — of the distinction between cash assistance and other safety-net programs.

He calls all of them “welfare,” they said.