The original five-year extension was to give lawmakers enough time to reform the Medicare reimbursement system so another "doc fix" would never have to be implemented. Waxman doesn't know if a 19-month extension will give lawmakers the time needed to address the issue.
Still, despite his disappointment, the congressman expects to support the bill.
"I'm going to look at the final package," he said, "Most likely I will vote for it."
The House is expected to vote on the legislation later Thursday, but it remains unclear if enough lawmakers will support the measure.
Sources told The Hill that Democratic leaders have had persistent problems in finding support for the bill because it adds to the deficit and increases taxes on businesses.
By bringing the bill to the floor, leaders hope rank-and-file members will have a harder time opposing the legislation and will back the measure.