With several of his campaign promises and his first budget now in the hands of Congress, President Trump is adding to perhaps the most critical week of his early presidency by putting his tax-reform plan into the mix.

Trump is set on Wednesday to announce his plan to cut taxes -- a top campaign promise along with building a border wall and repealing and replacing ObamaCare.

Mick Mulvaney, director of the White House Office of Management and Budget, told “Fox News Sunday” that Trump on Wednesday will give some indication of his proposed taxes rates and other details.

Trump to unveil tax cut he says could be biggest ever

However, he reiterated that a final plan won’t be ready until perhaps June and said he didn’t know whether the proposed cuts would add to the debt.

“I don't think we've decided that part yet,” Mulvaney said. “It's a balancing act in that you can either have a small tax cut that's permanent or a large tax cut that is short-term.”

Trump said Friday that his plan would include a "massive" tax cut for individuals and corporations.

Meanwhile, Congress returns Monday, after a roughly two-week recess, to try to pass a spending bill to avert a government shutdown Saturday.

The situation in the Republican-controlled Congress has been complicated by a potential showdown with Democrats over using the spending bill to pay for Trump’s proposed U.S.-Mexico border wall.

The so-called shutdown deadline falls on the same day as Trump’s 100th day in office, a largely symbolic marker of success for any U.S. presidency.

Despite Trump's dismissal that the 100-day marker is "artificial," the White House is planning a packed week of activities leading up to Saturday.

Trump will sign executive orders on energy and rural policies, dine with Supreme Court justices, meet with the president of Argentina and travel to Atlanta for a National Rifle Association event. Top aides will also fan out around the country to promote the administration.

Mulvaney and other White House aides stressed on Sunday talk shows that funding the wall and a vote to repeal and replace President Barack Obama's signature health care law were priorities. But they also suggested a shutdown could be avoided.

House Minority Leader Nancy Pelosi, D-Calif., on Sunday suggested that Trump has problems with Republicans not supporting the wall, which she called "immoral" and "expensive."

"Democrats do not support the wall," she said on NBC’s “Meet the Press.” "Republicans on the border states do not support the wall. ... Republicans have the votes in the House and the Senate and the White House to keep government open. The burden to keep it open is on the Republicans.”

Trump would like to revive House Republicans' failed effort earlier this year to replace ObamaCare.

He also hopes to use the $1 trillion catchall spending bill to salvage victories on his campaign-promised border wall, a multibillion-dollar down payment on a Pentagon buildup and perhaps a crackdown on so-called sanctuary cities that refuse to cooperate with immigration enforcement by federal authorities.

But so far, negotiations have proven difficult, with disputes over the wall and health law subsidies to help low-income people afford health insurance.

House members received little information from leaders on a conference call Saturday.

White House Chief of Staff Reince Priebus told NBC that he believes the spending bill will include "something satisfactory" to reflect Trump's desire to build a wall.

The legislation would keep the government running through Sept. 30, the end of the budget year.

The president has repeatedly asserted that Mexico would pay for the wall, which he says is necessary to stop the flow of immigrants and drug smugglers illegally crossing the border.

Priebus also said Sunday that the White House would like to have a vote on the GOP-led ObamaCare overhaul plan bill in the House this coming week. But he insisted it didn't make too much difference to the White House whether the vote came next Friday or Saturday or Monday.

Trump tweeted a warning Sunday to Democrats, saying: "ObamaCare is in serious trouble. The Dems need big money to keep it going -- otherwise it dies far sooner than anyone would have thought."

House Speaker Paul Ryan, R-Wis., continues to suggest that averting a shutdown on non-essential government services is a priority over an ObamaCare vote.

The White House is eager to tout progress on the litany of agenda items Trump promised to fulfill in his first 100 days, despite setbacks including court bans on his proposed immigration limits and the high-profile failure earlier this year to repeal and replace ObamaCare.

The president said Friday he spent his first 100 days laying the "foundation" for progress later in his administration, including by building relationships with foreign leaders.

He will mark the 100 days on Saturday with a rally in Harrisburg, Pa.

The Associated Press contributed to this report.