President Donald Trump's presidential proclamation that will deny visas to immigrants who cannot prove they will obtain health insurance or can cover medical costs could exclude two-thirds of future immigrants, a new analysis found.

The proclamation is the latest and perhaps most significant action taken by the Trump administration to reduce legal immigration and may prove to be more restrictive than a separate, recent policy targeting legal immigrants who use public benefits. It will particularly affect lower-income immigrants.

Released quietly by the White House Friday evening, the proclamation will require immigrants to prove they will either obtain health insurance within 30 days of entering the country or prove they are able to cover "reasonably foreseeable" medical costs. Those who do not meet the requirement will be denied visas. Immigrants will also be denied a visa if they use the Affordable Care Act's subsidies to obtain insurance.

The rule may bar some 65% of would-be green card holders, an analysis by the nonprofit Migration Policy Institute found . The policy will not apply to asylum-seekers or temporary visas.

It will be a big barrier for immigrants who do not have a job offer that will provide health insurance or are not joining a spouse already in the U.S. who has health insurance they could join, says Julia Gelatt, a senior policy analyst at the Migration Policy Institute who conducted the analysis.

The health insurance system is difficult to navigate in a short period of time, Gelatt says, and individuals must make a certain amount of money to qualify for insurance through an ACA exchange without being eligible for subsidies.

The rule could create a de facto income test for immigrants and help achieve the Trump administration's long-term goal of shifting the legal immigration system to favor so-called merit-based immigration, rather than the immigration of those seeking to join family members who are already in the U.S.

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"It's consistent with this administration's push for so-called merit-based immigration to let in only people with high paying job offers and high educational achievement," Gelatt says. "This is perhaps the way to try to enact that type of policy without having a public debate or going through Congress."

The White House argues that uninsured immigrants create a financial burden on taxpayers and healthcare systems.

"Immigrants who enter this country should not further saddle our healthcare system, and subsequently American taxpayers, with higher costs," the proclamation says.

Immigration groups and advocacy organizations widely condemned the proclamation after it was issued.

The Trump administration has pushed for wholesale immigration reform aimed at decreasing family-based immigration and increasing merit-based immigration, but Congress has not acted on any such reform measures. Any bills aimed at reshuffling the legal immigration system would face almost impossible odds in the Democratic-controlled House.

In August, the administration finalized a new "public charge" policy that gives the government the authority to deny permanent legal status to immigrants who use public benefits like food or housing assistance, or those the government determines may be likely to use public benefits in the future. The policy is facing numerous court challenges.