Iowa Republican Sen. Chuck Grassley issued his own fact-check of President Trump Thursday, challenging his claims that his planned tax cut would be the biggest in U.S. history.

In fact, Grassley claimed, the Bush tax cuts that he helped pass in 2001 were bigger.

1/3 @reslDonaldTrump Ur tax cut will not be "largest in history of country" Here are the fact fr my own self Fact Checker — ChuckGrassley (@ChuckGrassley) October 12, 2017

Adjusted for inflation, the former Senate Finance Chairman claimed, the 2001 tax bill was a $1.87 trillion cut.

2/3 when I chaired Finance 2001 $1.35T adjusted for inflation =2016 $1.865T in tax cuts 2003 350B=2016 $468B 2005 $70B=2016 $88B — ChuckGrassley (@ChuckGrassley) October 12, 2017

Currently, the Senate is working toward a budget that would limit Trump's tax cuts to $1.5 trillion, athough that could be changed.

On Wednesday, Trump boasted at the White House that "I'm giving the largest tax cuts in the history of this country. In addition to that, there will be reform."

3/3 @realDonaldTrump regardless ur tax framework sets out badly needed cuts REFORM SIMPLIFICATION TO CREATE JOBS/ move byond ObamaSTAGNATION — ChuckGrassley (@ChuckGrassley) October 12, 2017

Although Grassley challenged the premise of Trump's claim, he commended him for the tax reform effort, saying that the tax framework "sets out badly needed cuts."