WASHINGTON (Reuters) - Some conservatives in Washington were fuming on Tuesday after an Obamacare rollback bill was tweaked by Republican leaders to delete a provision meant to crack down on illegal immigrants getting federal healthcare insurance coverage.

The development posed another problem for Republican leaders in the U.S. House of Representatives and President Donald Trump, who are trying to win congressional approval of the wider bill, the first big legislative test for Trump since taking office.

The provision would have allowed the Treasury Department to access data at the Department of Homeland Security to verify that healthcare tax credits went only to U.S. citizens and legal permanent residents, not to illegal immigrants.

In a largely procedural move, it was dropped from the bill after the Senate Parliamentarian determined that the Senate Finance Committee, which handles tax credits under the bill, does not have purview over the Department of Homeland Security.

Republican Representative Lou Barletta issued a statement on Monday evening, after the change was made, saying he could no longer support the bill, citing the obscure provision.

“I am concerned that the bill lacks sufficient safeguards for verifying whether or not an individual applying for health care tax credits is lawfully in this country and eligible to receive them,” said the Pennsylvania lawmaker.

The provision had been a key issue for conservative groups the Trump administration is trying to win over in its efforts to pass the bill known as the American Health Care Act, Trump’s plan to repeal and partly replace Obamacare.

Some conservatives have criticized the bill since Republican House leadership unveiled it earlier this month, dubbing it “Obamacare Lite” because they say it falls short in repealing Democratic former President Barack Obama’s 2010 healthcare law.

Republican leaders recrafted the bill on Monday in hopes of satisfying conservative and moderate critics. Trump visited Capitol Hill Tuesday seeking to win more support for the bill.

Lauren Aronson, spokeswoman for the tax-writing House Committee on Ways and Means, said the bill keeps the underlying policies of Obamacare that specify only U.S. citizens and legal permanent residents are eligible for the tax credits. The bill was expected to go before the full House for a vote on Thursday.