A day after the House of Representatives voted to expand the Affordable Care Act’s Medicaid program to millions of Americans, President Donald Trump said he was “wrong” to have advocated the expansion.

The GOP-controlled House on Tuesday voted to approve $5 billion in spending to pay for the expansion, which Trump initially touted as the best way to make the health care law affordable for low-income Americans.

The measure now heads to the Senate, where it will likely face a difficult path to passage.

Trump has repeatedly said the Medicaid expansion is “the most important thing” he’ll accomplish in his first 100 days in office, but many GOP lawmakers have questioned the value of the expansion because of its high cost.

Trump, however, has repeatedly insisted it is not necessary, pointing to the millions of people on Medicaid who would be able to enroll without the expansion’s help.