Treasury Secretary Steven Mnuchin said Thursday that the Trump administration has put forward a "very detailed plan" to reform the tax code, and that this plan is now being reviewed by lawmakers.

"There absolutely is a package," Mnuchin said in an interview at the Treasury with CNBC. He added that details would be released within a month.

"The House and the Senate are now socializing the plan with their members," Mnuchin said. "We're going to release a blueprint, and it's going to go to committee, and we're going to turn this into a bill that the president will sign."

President Trump traveled Wednesday to Missouri to promote the GOP push for tax reform, but didn't mention specifics. His speech elicited some Democratic criticism that the administration doesn't actually have a tax plan.

Pressed Thursday for details on items such as the target corporate tax rate, Mnuchin suggested that those aspects of the framework are still in flux.

"There's a bunch of different levers that we can move," he said. "And we've gone through the different levers and the scenarios, and these are the things that are being socialized with members, and we'll go through with the committees, and we'll see where we end up."

Nevertheless, in a separate interview with the Wall Street Journal, Mnuchin said that the administration is not just leaving the tax reform bill up to Congress.

Republicans aim to pass tax legislation before the end of the year, a goal that Mnuchin reasserted Thursday. Yet to do that, they would have to move very quickly from having no spelled-out plan or legislative text to having a final bill on Trump's desk.

To do that, they would likely first have to pass a budget in order to unlock the special procedural tool of reconciliation that would allow them to avoid a Democratic filibuster when the bill lands in the Senate. That would require reconciling several major disagreements about taxing and spending levels among Republicans.

Then, members would have to advance bills through the tax committees in the Senate and House and then the chamber floors. Many major points of contention that could slow or stall those processes have yet to be broached among lawmakers.