WASHINGTON — President Trump and Republican leaders have positioned their sweeping tax rewrite as a way to cut taxes on the middle class. But some top officials are now saying the plan may not benefit everyone in that income group.

The acknowledgment could complicate the administration’s ability to sell the tax plan, which is already facing questions from Republicans and Democrats over the cost and effect of the ambitious rewrite.

Those questions have gotten more pronounced after an analysis last week by the Tax Policy Center, which found that the plan could cost $2.4 trillion over the next decade, with the biggest benefits flowing to businesses and the wealthiest Americans. The analysis found that nearly 30 percent of those in the middle class could see their taxes increase as a result of changes to the deductions and exemptions many middle-class Americans rely on to lower their tax bills.

The breakdown is based on the framework released by the “Big Six” group of Republican lawmakers and administration officials, which did not include many details that could change the distributional impact, including an increase to the child tax credit and the potential for a higher tax rate on the richest Americans. Yet top officials acknowledged this weekend that a tax cut for everyone in the middle class may not be achievable.