Attorney General Bob Ferguson of the western US state of Washington Monday voiced his opposition to what he called an "anti-immigration" rule to be announced by the federal government in two days.

President Donald Trump's administration is scheduled to officially unveil on Wednesday a change to the "public charge" rule that would make it more difficult for low-income immigrants to obtain permanent residence or green cards in the United States.

The new policy would allow immigration officials to label any immigrant who uses one of many common public benefits, such as housing assistance, health care or food assistance, at any time in the future as a public charge, which would deny them their new or continuing legal status, Ferguson said.

"The Trump Administration's anti-immigrant agenda continues today with the announcement of proposed changes to the public charge rule," he said.

"These changes force legally present immigrant families into a Hobson's choice -- to sacrifice their dream of becoming Americans in order to provide health care, food or a roof over their children's heads, or let their families go without in order to remain in the country," he said.

The Washington attorney general, who is an outspoken critic of Trump's immigration measures, said this is a choice that immigrants should not have to make.

"We're taking a close look at whether or not this action is legal," he added.

Ferguson joined Washington Governor Jay Inslee and Seattle Mayor Jenny Durkan in sending a letter to criticize a proposed rule released by the Trump administration in December 2018.

The Washington officials asserted that the proposed rule would hurt residents in the state as more than an estimated 140,000 lawfully present Washingtonians, including many US citizen children, could lose health insurance as a direct result of the rule.