(CNN) A group of US citizens and a nonprofit organization sued the Trump administration this week over a proclamation that would deny visas to immigrants unless they can prove they will have health insurance.

The lawsuit , filed in US District Court in Portland, Oregon, claims that the proclamation will bar hundreds of thousands of immigrants from coming to the United States, and as a result, could separate families who are immigrating via family-sponsored visas.

"Indeed, the Proclamation is unprecedented in its scope and impact, the largest ever suspension on the entry of immigrants of its kind," states the lawsuit, which was brought by seven US citizens and Latino Network, an advocacy organization based in Oregon.

The proclamation is among a string of sweeping changes that could dramatically curb legal immigration to the United States. Earlier this month, President Donald Trump issued the proclamation, saying, " immigrants who enter this country should not further saddle our healthcare system, and subsequently American taxpayers, with higher costs."

Visa applicants will have to prove to consular officials that they will be covered by an approved health insurance within 30 days of entry into the US or possess the financial means to "pay for reasonably foreseeable medical costs." The new requirement could make it more difficult for people -- particularly ones without financial means -- to immigrate to the US.

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