WASHINGTON — The number of uninsured patients admitted to hospitals has dropped markedly this year, particularly in states that have expanded Medicaid coverage under the new federal health care law, a government report released Wednesday said.

The report from the Department of Health and Human Services said hospitals in states that have taken advantage of new Medicaid eligibility levels have seen uninsured admissions fall by about 30 percent.

The announcement is part of the Obama administration’s effort to persuade states that have declined to expand their Medicaid coverage to reconsider. So far, 27 states and the District of Columbia have agreed to provide Medicaid to people with income higher than poverty levels.

The report comes seven weeks before the start of a new round of open enrollment, a critical test for the health care law. Obama administration officials said both the Medicaid expansion and the law’s requirement that individuals obtain insurance had contributed significantly to the decrease in the number of uninsured Americans.

Other studies, however, also show that the rise in the newly insured under Medicaid has increased the number of patients seeking treatment in emergency rooms, one of the most expensive medical settings.

The Affordable Care Act expanded Medicaid to cover many low-income adults with no children living at home. They were previously ineligible in nearly every state. HHS estimates that about 8 million people have been added to the rolls of the program, which is jointly run by the federal government and the states.

The federal government is paying the states the entire cost of the expansion through 2016, gradually phasing down to a 90 percent share thereafter.