Trump pushes tax reform 'vision,' pressures Congress to deliver

— -- In an address kicking off his administration's push to overhaul the U.S. tax system, President Donald Trump outlined a broad set of proposals Wednesday, including lower rates and a reworking of the tax code, and placed pressure on Congress to deliver on the pledges to help the Republican party overcome a series of legislative setbacks early in his presidency.

"I don't want to be disappointed by Congress," said Trump in Springfield, Missouri as he lamented the GOP's failure on health care reform earlier this summer. "I think Congress is going to make a comeback. I hope so the United States is counting on it."

In the speech, which built on a message from his campaign rally in Phoenix last week, Trump promised to give Americans "the biggest tax cut in the history of our country," and said he aims to cut tax loopholes, lower business tax rates to 15 percent and craft a tax code that "creates more jobs and higher wages for Americans."

The president framed his plan as one that should attract bipartisan support. He specifically called attention to Missouri's Democratic Senator, Claire McCaskill, and gave instructions to those in attendance on how to proceed if the tax reform efforts failed.

"Your senator, Claire McCaskill, she must do this for you," said Trump. "And if she doesn't do it for you, you have to vote her out of office."

The last official paper from the White House on tax reform was a one-page outline of principles released by Treasury Secretary Steve Mnuchin and National Economic Director Gary Cohn from April, and congressional leaders have given little indication of when they might be ready to start voting on a bill.

The Mnuchin/Cohn proposal centered on reducing the seven current tax brackets to three, lowering taxes on business, eliminating tax breaks that mainly benefit wealthy individuals and encouraging the repatriation of overseas profits.

“Everybody has an agreement we are going to move this as fast as we can,” Mnuchin said during a briefing on April 27 in which he and Cohn talked through the proposal with reporters.

But since then, there are indications that even those pillars of the plan may have shifted. The New York Times reported yesterday that the original Mnuchin/Cohn proposal for a 15 percent corporate tax rate -- a number Trump touted Wednesday -- has shifted to the 20-to-25 percent range, and that a proposed 35-percent ceiling for income tax could be scrapped altogether, keeping the current 39.6 percent rate intact.

In response to a question about the White House’s reportedly evolving preferences, White House Assistant Press Secretary Natalie Strom told ABC News via email that, “the NYT reporting was based on their sources and we don’t confirm speculation. Those types of decisions are being hammered out in our collaborative process with Congress. We have nothing to release at this time.”

A senior administration official told reporters on a conference call Tuesday that the Missouri speech, billed as a tax reform specific event, will not flesh out any details.

“The specifics of the plan are extraordinarily important, but right now what the president is doing is casting a vision, and I think that's just as important,” the official, who insisted on anonymity to speak to reporters, said.

But Trump continues to refer to the tax overhaul plan in a much more concrete way.

“We're giving you the biggest tax cut in the history of our country,” he said during a campaign rally in Phoenix, Arizona last week.

"It's time to give Americans the pay raise that they've been looking for many, many years," he added Wednesday. "We have no choice. We must lower our taxes."

But Cohn made clear in an interview with the Financial Times last week that Congress, not the president, is taking the lead on crafting the actual tax reform legislation.

“In the next three or four weeks, the tax bill will be written in the Ways and Means Committee and Congress is going to own the writing of legislation -- that is key,” Cohn told the Financial Times.

But that committee, which will take the first stab at writing a bill, has not yet publicly said when it will introduce the legislation. A spokeswoman for the committee declined to say whether its members envision working on the same timeline as the one Cohn has suggested.

The White House also insists that the congressional drafting process should be a bipartisan exercise. But while the White House’s economic team has held regular meetings with Republicans, Senate Democrats have not been part of the conversation since May.

“There are no conversations being had between the administration and Senate Democrats,” an aide to Senate Finance Committee Ranking Member Ron Wyden told ABC.

Previous administrations have not been as deferential to Congress as Trump’s. Former President Ronald Reagan sent a 489-page proposal to Congress in 1985 to make his thoughts on tax reform clear.

But it’s possible that congressional leaders prefer that Trump focus on his PR campaign rather than delve into the nitty-gritty of tax policy specifics.

During an interview with the Washington Examiner last week, House Speaker Paul Ryan, who has been doing his own tax reform road show around the country, suggested that he doesn’t mind the White House being occupied with other issues, saying it "actually helps us concentrate our minds and focus on getting this done, especially because of the acrimony that's in America and the distraction."

ABC News' John Parkinson and Adam Kelsey contributed to this report.