Mnuchin: Trump's corporate tax rate goal may not be achievable

"I don't know if we'll be able to achieve that, given the budget issue," Mnuchin said at an conference hosted by CNBC. "But we're going to get this down to a very competitive level, and what the exact number is less important. And what's more important is making sure we have a competitive system."

Mnuchin's comments are similar to remarks that Speaker Paul Ryan (R-Wis.) made last week. Ryan said that "the numbers are hard" to make a 15-percent rate possible, and that he's shooting for a rate in the low-to-mid 20s.