WASHINGTON — House Republicans, straining to make last-minute changes to their far-reaching tax proposal, on Tuesday delayed the rollout by a day after they failed to finalize the details.

The plan pushed by President Donald Trump and Republican leaders in Congress is a top legislative priority. The details originally were to be unveiled on Wednesday, but that was delayed until Thursday, said Rep. Kevin Brady, R-Texas, chairman of the tax-writing Ways and Means Committee.

The committee had worked throughout the day and evening to produce a plan for the first overhaul of the nation’s tax code in three decades.

“We are making excellent progress. We are very close,” Brady told reporters late Tuesday night. “A lot of work remains with the drafters, they are continuing to work through the night. We are moving forward.”

At the White House, an official said Trump looked forward to seeing legislation this week, adding the administration was confident the delay wouldn’t affect the ultimate timing of the bill. Brady said his panel plans to vote on the bill next week.

Although they had settled on some key details — such as a cut in the corporate tax rate to 20 percent and maintaining the top personal income tax rate for the wealthy of 39.6 percent — other elements still had to be resolved, including the income levels for the tax brackets.

Trump has intensified his lobbying for the nearly $6 trillion tax overhaul plan, seeking a major legislative achievement after the collapse of the health care repeal. Republicans see taxes as a political imperative that will decide whether they keep their congressional majorities in next year’s midterm elections.

The president set an ambitious timetable and predicted a grand signing ceremony before Christmas at “the biggest tax event in the history of our country.”

Late Tuesday, Trump renewed his cheerleading on Twitter.

“The Republican House members are working hard (and late) toward the Massive Tax Cuts that they know you deserve. These will be biggest ever!”

The plan originally unveiled by Trump and congressional Republicans called for shrinking the number of tax brackets from seven to three, with respective tax rates of 12 percent, 25 percent, 35 percent. That plan drew immediate criticism from Democrats, who complained it was too favorable to the wealthy and undermined Trump’s rhetoric about it benefiting the middle class.

The current Republican plan calls for nearly doubling the standard deduction used by most average Americans to $12,000 for individuals and $24,000 for families, and increasing the per-child tax credit. In addition to slashing the corporate tax rate, it also seeks to repeal inheritance taxes on multimillion-dollar estates, a big break for the wealthy.

Brady did not answer directly when he was asked — while leaving House Speaker Paul Ryan’s suite Tuesday — whether the drop in the corporate tax rate would happen immediately. But, he said: “I want as much growth right from Day One as I can.”

Trump intensified his lobbying for the tax overhaul plan even as its shape was still under negotiation by the Republicans on Capitol Hill.

“The process is complicated but the end result will not be that complicated. It’s going to be: People are going to pay less tax by a lot, companies are going to pay less tax by a lot – that’s a big difference — and companies are going to start rebuilding and they’re going to stay here,” Trump said in the Roosevelt Room, where he was joined by the heads of more than a dozen business and trade allies.

Trump said he’s directing Treasury Secretary Steve Mnuchin, White House economic adviser Gary Cohn and other administration officials to stay behind when he heads for Asia on Friday so they can help sell the tax proposal. The White House said Ivanka Trump, the president’s daughter and adviser, had canceled plans to accompany the president to China and South Korea to help push the package.

The president said he was hopeful the House will approve the tax bill by Thanksgiving. But his overly optimistic timetable didn’t address the concerns of lawmakers from states such as New York and New Jersey who have opposed a proposal to eliminate the federal deduction for state and local taxes, arguing it would hurt their constituents and subject them to being taxed twice.

A battle continues over contributions to 401(k) retirements accounts. The financial industry and some Republican lawmakers insist that the GOP plan not change the tax benefits of the popular savings vehicles, as has been floated by GOP leaders.

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Associated Press writers Andrew Taylor, Marcy Gordon, Erica Werner and Jill Colvin contributed to this report.