TRENTON, N.J. — Gov. Chris Christie said Monday that more than 500,000 New Jersey residents now have health insurance coverage under Medicaid as part of the expansion under the Affordable Care Act.

The Republican governor’s announcement came during a statehouse news conference and as Republicans across the country, including GOP presidential candidate Donald Trump, campaign for office under a banner of “repeal and replace” of the 2010 law.

Christie says 566,655 residents now have the coverage, bringing the number of insured residents under the state’s public health insurance program to 1.7 million. He says contrary to “naysayers” of the expansion that it would raise costs, the average expenditure per beneficiary in New Jersey decrease from $9,690 in fiscal year 2014 to $8,940 in fiscal year 2015.

He also said the state’s share of expenditures dropped from 45 percent in 2014 to 39 percent in 2015.

The announcement comes as Trump has said he would end “Obamacare” and replace it with something better. A recent nonpartisan analysis found that the plan Trump has outlined would make 18 million people uninsured.

Christie said Monday that the Medicaid expansion was just one part of the legislation and that Republicans have included in their own proposals.

He credited his decision to expand Medicaid with helping to insure more people, but he also criticized the federal government, which he said he did not trust and that future New Jersey governors should be able to evaluate the state’s partnership with federal government if it makes financial sense.

“I am for Medicaid expansion. But I am not for Medicaid expansion at any price,” Christie said.

Christie opted three years ago to expand Medicaid despite Republican opposition to the health care law. At the time, Christie said he thought the law was not right for the country or the state, but that if New Jersey did not accept federal cash to expand its program the money would just be spent in other states.

The expansion allowed adults without children and an income of up to 138 percent of the federal poverty level to apply for coverage.

Linda Schwimmer, the president of nonpartisan, nonprofit New Jersey Health Care Quality Initiative, said the announcement did not come as a surprise to the health care community.

She called the expansion the “right decision” for the state, but said that it’s likely the falling number of uninsured could plateau because the federal government’s reimbursement will begin to taper from 100 percent coverage to as low as 90 percent.