Asked by CNN's Dana Bash on "State of the Union" if he was abandoning his long-stated vow to pass a revenue-neutral tax overhaul, McConnell said, "We're not."
McConnell argued the tax proposal, the framework of which includes
large tax cuts for the top earners and corporations, would spur enough economic growth to pay for itself and that the $1.5 trillion deficit figure did not take into account the kind of growth he expects.
"I actually think it's a fairly conservative estimate of how much growth we're likely to get out of this pro-growth tax reform," McConnell said.
The budget vote on Thursday cleared a key hurdle for Republicans on tax reform passing narrowly through the Senate, by a vote of 51-49. The lone dissenting Republican was Sen. Rand Paul, who hails from McConnell's state of Kentucky and voted against the bill because he said it did not cut spending enough.
In Sunday's interview, McConnell did not say if he could guarantee tax reform would not add to the deficit, but went on to predict the GOP would successfully enact their plan.
"We're going to score a big legislative accomplishment on tax reform," McConnell said.
In a separate interview on the same program, Ohio Democratic Sen. Sherrod Brown said he did not see President Donald Trump in lockstep with McConnell on the tax issue just yet.
Brown argued Trump's stated goal of reducing taxes for the middle class was at odds with the plan McConnell was working on, and contrary to what most thought, he said that after meeting with the President that Trump might pursue a different path on taxes.
"Most of my progressive colleagues think that Trump will throw in with McConnell because he has more often than not on these big economic issues," Brown said. "I'm still hopeful from that conversation. I'm going to keep pushing for it."
Trump has talked up his desire for historic tax cuts and an overhaul of the system. The framework of the GOP tax plan came as a product of negotiations between the administration and Republican leaders on Capitol Hill, and Trump continues to use his White House perch to push that plan.
White House budget director Mick Mulvaney, speaking on CBS' "Face the Nation," pointed to tax reform as an area where he hoped Republicans would translate broad campaign promises into reality, lamenting his party's inaction on a range of issues, especially health care.
"We have to start keeping our promises," Mulvaney said.
The Senate's successful budget vote on Thursday was "a big step" toward keeping the GOP's promise on taxes, he said.