Sen. Bernie Sanders, I-Vt., announced his opposition to President Joe Biden’s pick to lead the Food and Drug Administration on Tuesday, citing the nominee’s ties to the pharmaceutical industry.

Sanders, a senior member of the Health, Education, Labor and Pensions Committee, said on Twitter that he will oppose the nomination of Dr. Robert Califf, a cardiologist at Duke University who briefly served as FDA commissioner at the end of the Obama administration.

“We need leadership at the FDA that is finally willing to stand up to the greed and power of the pharmaceutical industry,” Sanders said. “In this critical moment, Dr. Califf is not the leader Americans need at the agency and I will oppose his nomination.”

At his confirmation hearing Tuesday, Sanders told Califf that since he had left government, “you have made several hundred thousand dollars from pharmaceutical companies and have received consulting fees from Merck, Biogen and Eli Lilly.”

Sanders cited financial disclosure forms that show that Califf owns up to $8 million in stock of major pharmaceutical companies.

Biden nominated Califf last month. He has worked with Google’s parent company, Alphabet Inc., and was the FDA’s deputy commissioner overseeing medical and tobacco products from 2015 to 2016.

“At a time when the American people are outraged by the high cost of prescription drugs, deeply disturbed about what happened with Purdue and OxyContin, what kind of comfort can you give to the American people when you have been so closely tied to the pharmaceutical industry yourself?” Sanders asked Califf. “How are they going to believe you are going to be an independent and strong voice against this enormously powerful special interest?”

Califf cited the Biden administration’s ethics pledge, which he said is very “stringent.”

“They’ve reviewed my status, I’ve agreed to the ethics pledge, and FDA and HHS have excellent staff whose job it is to make sure that the ethics pledges are adhered to,” Califf said, referring to the Department of Health and Human Services.

Sanders isn’t the only senator to oppose Califf. Joe Manchin, D-W.Va., said the FDA also needs a change in culture to fight the opioid epidemic.

“I have made it abundantly clear that correcting the culture at the FDA is critical to changing the tide of the opioid epidemic,” Manchin said in a previous statement. “Instead, Dr. Califf’s nomination and his significant ties to the pharmaceutical industry take us backwards.”

The Centers for Disease Control and Prevention reported 100,000 overdose deaths in the U.S. in the 12 months that ended in April, an increase of 28.5 percent from the previous 12 months.

It’s unclear whether opposition from Sanders and Manchin would be enough to sink Califf’s nomination in the 50-50 Senate.