Don’t expect President Donald Trump to lay out his specific demands for an emerging Republican tax overhaul plan when he delivers his first major speech on the subject Wednesday.

Senior White House officials made clear Tuesday that the president is traveling to Springfield, Mo., not to talk policy — but to take his “optimistic” case for simplifying the federal tax code and lowering rates for businesses and middle-class taxpayers.

A senior White House official described the remarks Trump will deliver at a manufacturing facility in Springfield as a “‘why’ not a ‘how’ speech.”

Trump’s aides say the event will mark the beginning of a sales pitch they expect will last well into the fall and take the president across the country.

It expands on remarks he made in Phoenix last week promising “the biggest tax cut in history” and lower tax rates for businesses that would boost the economy.

Republicans plan to use the budget reconciliation process to move the tax bill through Congress, which would only require 51 votes for Senate passage.

That strategy makes it likely Trump could visit only GOP-heavy states and, possibly, swing states he won last year to woo GOP senators who might be on the fence about the package now being devised by GOP congressional leaders and administration officials.

Trump’s focus is, in part, “dedicated to communicating directly to the American people on why tax reform is needed,” the senior White House official said Tuesday.

Trump aides have said the president has no plans to get into specifics such as the corporate tax rate, which he previously has said should be lowered from 35 percent to 15 percent.

The senior official told reporters the White House knows the policy specifics, which are still under negotiation, are important. But administration officials also view the sales pitch as crucial.

“What the president is doing now is casting a vision [of] what kind of America do we want to live in?” the official said.

Aides say Trump’s policy goals are unchanged from a one-page set of principles released in April. It called for a 15 percent corporate rate that Trump contends would make U.S. businesses more competitive. The proposal also called for a tax cut for middle-income Americans by increasing their standard deduction.

But its apparent effect on the deficit and the exclusion of a House GOP-favored border adjustment tax mean continued negotiations between Trump’s team and Republican tax-writers could get bumpy.

Trump has decided the time has come for him to “really get out there and talk about [why] tax reform is needed,” the senior White House official said.

The president’s speech will have two themes: easing the “burden” on American companies and helping middle-income Americans keep more of their earnings.

Expect Trump to “be explicit in calling for businesses to hire and grow in America,” the senior official said, signaling the president wants to use a carrot-and-stick approach with business leaders on a tax overhaul.

He also likely will mention the idea of closing tax loopholes, which is something that “cuts along bipartisan lines,” the senior official said.

The loopholes will be cited by the president during his speech as an example of how “the economy is rigged” — a major theme of his populist 2016 campaign.

To gin up public support for a tax bill, Trump’s campaign “will include additional travel and other events,” a White House official said Monday.

No details were given on future trips.