President Donald Trump's administration is planning to make it harder to get food aid through the federal government's big grocery assistance programme that serves about one in 10 Americans.

The administration says the proposed rule would close a loophole by no longer allowing some people who receive benefits under the federal Temporary Assistance for Needy Families programme to automatically qualify for the separate Supplemental Nutrition Assistance Program too.

About 6.3 million people could lose eligibility for SNAP by the 2029 fiscal year if the proposed change takes effect, according to the US Department of Agriculture, which administers the programme. That is on top of 5.5 million people who already have lost SNAP benefits over the past year.

The plan is laid out in a proposed rule published Tuesday on how to run SNAP, and the government is seeking public comment until next month. If it is accepted, the rule would not take full effect for about two years.

At issue are two separate federal programs. The TANF programme provides federal grants to states, which set their own eligibility rules for distributing cash and other benefits to low-income families with children. The incomes of recipients vary by programme and state.

Federal guidelines generally limit SNAP food benefits to those earning less than 130 per cent of the poverty level, a little over US$1,700 (S$2,100) monthly for an individual or nearly US$3,600 for a family of four. To reduce duplicative paperwork, the federal government allows people who already receive TANF benefits to automatically qualify for SNAP — though they still have to apply.

Some states have used that automatic eligibility to expand SNAP benefits to people who might not otherwise qualify. In 2009, President Barack Obama's administration encouraged states to provide people a minimal TANF-funded benefit, such as an informational pamphlet or telephone hotline, as a way of qualifying them for the food programme.

Forty-one states and the District of Columbia have some form of broad-based categorical eligibility for SNAP, according to a USDA report from last year.

The first Trump administration proposed to clamp down on such tactics in 2019. But that proposal was withdrawn by President Joe Biden's administration in 2021.

"Simply put, we did not want to remove millions of people from the programme, particularly working poor or children," said Stacy Dean, a former USDA official under Biden who now is executive director of the Global Food Institute at George Washington University.