Federal Reserve Chair Janet Yellen denied allegations from Donald Trump that the Fed is keeping interests rates low to support the Obama administration, saying it is an independent agency.

Speaking at a news conference Wednesday afternoon, Yellen said politics do not play into the Fed’s decisions. The Fed decided to leave interest rates unchanged on Wednesday, in a predictable decision that indicates improvements in the economy, but not enough strength to bear higher borrowing costs.

“I can say emphatically that partisan politics plays no role in our decisions about the appropriate stance of monetary policy,” Yellen said.

Trump on Monday said Yellen should be “ashamed” of keeping interests rates low. Although he has previously said he supports her policies, the Republican nominee said in April that he would replace Yellen if elected president.

“She’s obviously political and doing what Obama wants her to do, and I know that’s not supposed to be the way it is,” Trump told CNBC.

Yellen said the Fed is trying to “decide what the best policy is to foster price stability and maximum employment to manage the variety of risks that we see as affecting the outlook.”

“We do not discuss politics at our meetings and we do not take politics into account in our decisions,” she said.