(CNN)Nearly six months into a presidency fully engulfed in a battle against a global pandemic, President Joe Biden is in a standoff with senators in his own party over who should lead the US Food and Drug Administration, a key post in the fight against Covid-19 -- with no indication the White House will name a permanent commissioner anytime soon.
Dr. Janet Woodcock, a career official since 1986, has been serving as acting head since January but has come under fire from several Senate Democrats over the agency's role in the opioid crisis and is no longer considered the front-runner, multiple sources tell CNN. However, it is unclear who else is in the running to serve as the agency's head.
While administration officials had hoped the opposition to Woodcock would abate, it has only grown on Capitol Hill around the FDA's approval of a controversial new Alzheimer's drug.
Officials are showing no sense of urgency in filling the position and blame the lack of a nominee on the intricacy of the role and finding a candidate who understands the ins and out of the agency.
"We have strong acting leadership in place that is playing an important role in our Covid-19 response and beyond, and look forward to sharing a nominee with the requisite expertise and leadership for this job," a White House official told CNN.
But critical issues -- including boosting vaccinations and battling Covid-19 variants -- plague the country and Biden is without a key position permanently filled to help battle both the logistics of the pandemic and the perception that his administration is not operating at capacity.
Lawmakers on both sides of the aisle have called on the administration to fill the role permanently.
"I have the greatest respect for Janet Woodcock. She is leading the FDA ably, and I think she has all of the qualifications needed for this moment, but we need a fully confirmed person in that role," Republican Sen. Richard Burr of North Carolina, the top Republican on the Senate Health, Education, Labor and Pensions, said in a recent committee hearing.
A Burr spokesperson told CNN that there was "no substitute for having a permanent, Senate-confirmed FDA commissioner in place. Sen. Burr continues to call on the Biden administration to nominate a qualified individual to fill this critical role."
Woodcock is a controversial figure with Democrats, and multiple sources tell CNN they do not believe she will be nominated to head the FDA, despite having supporters within the agency and the White House.
Woodcock's critics include Democratic senators from states hit hard by the opioid epidemic such as Maggie Hassan of New Hampshire, Ed Markey of Massachusetts and critical swing vote Joe Manchin of West Virginia. They partly blame the crisis on the FDA and the division Woodcock led -- the Center for Drug Evaluation and Research -- for its approval of new addictive opioids and lax restrictions on painkillers.
According to a source with knowledge, Hassan raised her concerns with Biden and the administration, particularly that an FDA commissioner needs to be someone who will act independently from the industry that he or she regulates.
"The rallying around Ms. Woodcock's nomination that we've seen from big pharma should give everyone real pause," Hassan said in a statement to CNN. "I have concerns about her role in approving and labeling opioid-based medications, and whether she has learned from and taken action to correct the FDA's mistakes in that area."
Many experts believe that Biden will ultimately choose someone with a less controversial history.