WASHINGTON >> President Donald Trump and Senate Republicans scrambled today to make changes to a Republican tax bill in an effort to win over holdout GOP senators and pass a tax package by the end of the year.

In a morning tweet, the president said, “With just a few changes, some mathematical, the middle class and job producers can get even more in actual dollars and savings.”

Trump and Senate leaders are trying to balance competing demands, as some senators fear the package would add to the nation’s mounting debt, while others want more generous tax breaks for businesses. In a boost for the legislation, Republican Sen. Rand Paul of Kentucky said he would back the measure.

Trump hosted Republican members of the Senate Finance Committee at the White House Monday.

Afterward, Sen. John Cornyn of Texas, the No. 2 Republican in the Senate, said the plan is to vote on the current tax bill this week, then work out the differences between the Senate bill and one passed by the House earlier this month.

“We think the Senate bill made some substantial improvements over the House bill but we’ll work through those when we get to a conference committee with the House,” Cornyn told reporters.

But as of Monday, GOP leaders were still trying to round up the votes in the Senate to pass the bill.

“We always have to deal with everybody. It’s not any one particular person,” said Sen. Orrin Hatch, R-Utah, chairman of the Finance Committee. “These are tough times, these are tough issues, they’re hard to deal with and we’ve had to deal with them.”

Trump suggested he is open to making unspecified changes to the way millions of “pass-through” businesses are taxed, a sticking point for some lawmakers. These are businesses in which profits are passed onto the owners, who report the income on their individual tax returns. The vast majority of U.S. businesses, big and small, are taxed this way.

Sen. Ron Johnson, R-Wis., has already declared his opposition to the current bill, saying it doesn’t cut business taxes enough for these types of partnerships and corporations. Johnson gets substantial income from such companies, including a manufacturer he helped found in Wisconsin and a commercial real estate company, according to his financial disclosure statements.

Trump and Republicans have set as a vital political goal the passage of tax overhaul legislation by the end of the year. The House recently passed a $1.5 trillion bill. Senate GOP leaders hope to muscle their bill through this week.

Trump was meeting Monday with five members of the Senate Finance Committee who are on board with the GOP plan. He will travel to Capitol Hill Tuesday to lobby Republican senators personally.

Republicans have only two votes to spare in the Senate, where they hold a 52-48 edge.

Their package blends a sharp reduction in top corporate and business tax rates with more modest relief for individuals.

Democrats say the package would mainly help corporations and the rich. Their argument was bolstered by a new congressional analysis that says the Senate bill would leave many low- and middle-income families worse off, while the wealthy would get big benefits. The analysis was done by the nonpartisan Congressional Budget Office.

In signaling his support, Paul wrote in an op-ed on Fox News: “I’m not getting everything I want — far from it. But I’ve been immersed in this process. I’ve fought for and received major changes for the better — and I plan to vote for this bill as it stands right now.”

Holdouts include Republican Sen. Susan Collins of Maine, who has objected to a provision in the Senate bill repealing the requirement under the “Obamacare” program that everyone have health insurance. Collins has said that issue should be dealt with separately from the effort to overhaul the tax code.

GOP Sens. Bob Corker of Tennessee and John McCain and Jeff Flake of Arizona worry that the package will add to the nation’s mounting debt.

Corker’s office said he spent the Thanksgiving weekend on the phone with Senate colleagues and administration officials trying to find a path forward.

GOP leaders are working with on a potential revenue “backstop” in case the party’s tax cut legislation fails to produce hoped-for levels of growth and tax receipts.

Oklahoma Sen. James Lankford said he and other Republicans are working on “just-in-case options” to add to the measure during Senate floor debate this week. He appears to be talking about a mechanism that could automatically force tax rates back up if revenues fall short.