President Donald Trump believes tax reform, a key campaign plank that has boosted the business community’s expectations for his presidency, will be done this year.

Asked by Fox News’ Bill O’Reilly if Americans should expect a tax cut this year, Trump said he was optimistic.

“I think so, yes,” Trump said in a wide ranging interview that aired Sunday, ahead of the Super Bowl. “And I think before the end of the year I would like to say yes.”

The president’s promise comes as some investors and analysts have begun to rethink the optimism that helped propel markets in a broad-based “Trump rally.” Over the weekend, Goldman Sachs warned that economic and political realities were conspiring to undermine the market’s high hopes—and Trump’s lofty ambitions.

A lack of consensus on how to implement a controversial border adjustment tax appears to be dividing Republicans, something Goldman pointed to in its analysis.

Trump ran on a platform of across-the-board income and corporate tax cuts, saying that he believes the change will boost economic activity and job creation. So far, though, Congress has spent little time on the effort amid a push to repeal the Affordable Care Act.

Trump has touted tax cuts in meetings with business leaders since he took office, saying they encourage companies to keep operations and jobs in the United States. Hopes for that policy change, as well as potential infrastructure funding, helped to power a stock market rally in the weeks after Trump’s election in November.

House Speaker Paul Ryan recently said Republican lawmakers will try to start pushing through tax reform and infrastructure bills in the spring.

“It’s just the way the budget works that we won’t be able to get the ability to write our tax reform bill until our spring budget passes, and then we write that through the summer,” Ryan said Thursday on “Fox and Friends.”

Trump has called for slashing the corporate tax rate to 15 percent from 35 percent. Ryan’s proposal calls for a 20 percent corporate rate.

–CNBC’s Javier E. David contributed to this article.