(CNN) President Donald Trump on Wednesday delivered his opening pitch on tax reform, framing the effort in populist terms saying Republican plans to overhaul the tax code would be a boon for lower- and middle-class Americans.

But Trump offered only broad outlines of what the tax code would look like if his tax reform gambit succeeds, as GOP congressional leaders and the White House have yet to reach an agreement on the details of the tax plan. Trump will meet with congressional leaders to hammer out those details on Tuesday, a White House official said.

"We're here today to launch our plans to bring back Main Street by reducing the crumbling burden on our companies and on our workers," Trump said in Springfield, Missouri. "The foundation of our job creation agenda is to fundamentally reform our tax code for the first time in more than 30 years."

Even as he laid out his tax reform pitch in broad strokes, Trump sought to turn up the pressure on members of Congress to get behind his still-undetailed effort and he called out Missouri's Democratic Sen. Claire McCaskill.

"She must do this for you and if she doesn't do it for you, you must vote her out of office," Trump said. "She's gotta make that commitment. If she doesn't do it, we can't do this anymore."

Broad outlines

Trump's pitch leaned heavily on the economic benefits he said tax reform could deliver and aimed to get ahead of Democratic criticism that Trump's tax reform plans would disproportionately benefit the wealthiest Americans, as independent tax experts have estimated.

The criticism still flowed in, with Democratic National Committee Chairman Tom Perez saying that Republican tax reform proposals "would overwhelmingly benefit the super-rich and corporations over hardworking Americans."

"Under this plan, the richest Americans would become even richer at the expense of middle-class families," Perez said in a statement. "Democrats believe that not one penny of tax cuts should go to the 1%. Instead of trying to benefit themselves, Trump and Republicans should work with Democrats to enact real, bipartisan tax reform for the middle class."

Trump began his remarks by sending prayers to the victims of Hurricane Harvey in Houston, calling the storm "deeply tragic" and telling those who lost loved ones in the storm that "all of America is grieving with you and our hearts are joined with you forever"

"We will endure and we will overcome," he said, praising first responders who "saved countless lives."

Trump's speech kicked off in earnest the effort of selling tax reform, which Treasury Secretary Steven Mnuchin said last week he hopes to get to the President's desk by the end of the year.

As of yet, Trump's plan remained stuck in broad outlines: simplifying the tax code, creating a more competitive tax code, delivering tax relief for the middle class and repatriating offshore profits. Trump also said he would like to bring the business tax rate down to 15%, a figure that has been met with resistance by congressional leaders who see it as too low.

But Trump's mission on Wednesday, administration officials said, was to frame the debate, not lay out a detailed proposal.

That effort comes as he and his administration have raised the need for tax reform in fits and starts since the early days of his presidency. Mnuchin initially set the end of August as a timetable for passage of tax reform efforts and, in April, the administration released several topline numbers of its proposal. But the White House and Congress have failed to sync up in their ambitions for reform amid disagreements and as lawmakers remained stuck on failed efforts to repeal Obamacare.

Now, the White House faces a jam-packed fall legislative calendar that includes deadlines to avert a government shutdown and raise the debt ceiling -- and now added pressure to pass a disaster assistance package for recovery efforts in the wake of Hurricane Harvey.

Timing

Trump's attempt to turn the national conversation to tax reform comes as the spotlight is firmly fixed on the disaster still unfolding in Texas and Louisiana, where hurricane damage and flooding continues to sending tens of thousands of people from their homes.

Trump made his first trip to Texas on Tuesday and is expected to return to the area on Saturday. A White House official said Trump would again address the disaster during his tax reform remarks.

Trump's first attempt at applying the bully pulpit to his tax reform push also comes on the heels of internal strife over the President's response to the violence in Charlottesville, Virginia, which prompted Trump's top economic adviser Gary Cohn -- who along with Mnuchin has helmed tax reform efforts at the White House -- to publicly rebuke the White House's response to the white supremacist rally there.

"I believe this administration can and must do better in consistently and unequivocally condemning these groups and do everything we can to heal the deep divisions that exist in our communities," Cohn told the Financial Times in a striking rebuke of a president by one of his top advisers.

Cohn said he had decided to remain at the White House and administration officials have said he has remained focused on the tax reform push.

But Trump on Wednesday raised eyebrows when he thanked several members of his team by name and left Cohn -- who traveled with Trump to Missouri on Wednesday -- off the thank you list.

"Anybody I forget?" Trump said, before moving on with his speech.

White House press secretary Sarah Huckabee Sanders pushed back on those drawing any conclusions from the omission, saying that while Trump "regularly mentions Cabinet members," he "rarely mentions staff."

But Trump on Wednesday did acknowledge two members of his staff, his chief of staff John Kelly and daughter Ivanka Trump, one of his top advisers.

Sanders insisted Trump and Cohn are continuing to work closely on tax reform.

"They're both working hard and extremely committed to providing tax relief for middle class America," Sanders said. "Gary Cohn is one of the people leading that effort for him and he will continue to do that."

The Trump administration outlined the broad strokes of its proposal for tax reform in April, proposing slashing the number of tax brackets from seven to three and bringing the corporate tax rate down to 15%. It also called for income tax brackets to be set at 10%, 25% and 35% -- the latter for the wealthiest Americans, down from the current 39.6% rate.

But since the administration released that outline, it agreed to give the reins on tax reform to Congress -- working with leaders as part of the "Group of Six" to come up with a single Republican tax reform plan that leaders hope will earn broad support in Congress.

Still, Trump is expected to play a much more public role in driving support for tax reform, taking to the road more frequently to hammer the benefits of tax reform than he did during Republicans' failed effort to repeal Obamacare.

Tax reform was at the core of Trump's economic proposals during his campaign and aides said it's an issue Trump feels he can effectively pitch to the public.