Rep. Ken Buck on Wednesday sent a letter to President Biden's attorney general pick Judge Merrick Garland asking him to keep on the federal prosecutor who is in charge of the probe into Hunter Biden -- or otherwise appoint a special counsel. 

The request by Buck, R-Colo., first obtained by Fox News, follows a notice from the Biden administration earlier this month requesting that Trump-appointed U.S. attorneys resign to transition the Department of Justice (DOJ) to prosecutors picked by the new president.

One exception to that was Delaware U.S. Attorney David Weiss, who is overseeing the federal tax investigation into Hunter Biden. White House press secretary Jen Psaki said that decision was "made in order to fulfill [Biden's] promise of maintaining independence."

Buck's letter Wednesday requests that Garland, who will oversee all federal prosecutors if confirmed, follow Biden's lead in keeping Weiss employed. 

Hunter Biden, the son of new US President Joe Biden, attends his father's inauguration as 46th US President on January 20, 2021, at the US Capitol in Washington, DC. (Photo by JONATHAN ERNST / POOL / AFP) (Photo by JONATHAN ERNST/POOL/AFP via Getty Images) (Getty Images)

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"I write to request that, during your Senate confirmation hearings, you commit to keeping David C. Weiss as the United States Attorney for the District of Delaware until his office completes its ongoing investigation into Hunter Biden," Buck wrote. "Mr. Weiss brings over a decade of leadership experience as First Assistant U.S. Attorney, Acting U.S. Attorney, and Interim U.S. Attorney for the District of Delaware, and has conducted this investigation with the utmost professionalism and discretion."

Buck continued: "This probe is critical to defending the integrity of our republic and ensuring the Biden Administration will not be the subject of undue foreign interference... Should you wish to remove Mr. Weiss from his post before he brings this investigation to a close, I urge you to commit to appointing a Special Counsel to complete the investigation."

Senate Republicans had already indicated that they intend to press Garland, a judge on the D.C. Circuit Court of Appeals and former President Barack Obama's one-time Supreme Court nominee, on how he would handle the Hunter Biden probe. 

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"Americans deserve to know that this investigation will not be hampered in any way by the change in administrations, and the attorney general nominee should make this point clear," a spokesperson for Senate Judiciary Committee member Sen. Chuck Grassley, R-Iowa, previously told Fox News. "So yes, you can expect that Sen. Grassley will be asking about his role in this investigation."

"It is very likely the topic is raised," a spokesperson for Sen. Lindsey Graham, R-S.C., also previously told Fox News.

Hunter Biden's foreign entanglements have been a source of controversy for the Biden administration in its early days. 

Earlier this month Psaki said that the younger Biden is still "working to unwind his investment" his investment with a Chinese equity fund despite a promise from President Biden that his family would not hold foreign investments during his presidency. 

In this Jan. 7, 2021, file photo President-elect Joe Biden's nominee for Attorney General Judge Merrick Garland speaks during an event at The Queen theater in Wilmington, Del. (AP Photo/Susan Walsh, File)

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"No one in my family will have an office in the White House, will sit in on meetings as if they are a cabinet member, will, in fact, have any business relationship with anyone that relates to a foreign corporation or a foreign country," Joe Biden said before the presidential election.

But Biden has so far apparently kept his promise to stay out of any DOJ matters involving his family. Buck said Wednesday that Biden's AG pick should do the same. 

"Any action to alter the investigatory process on your part could taint the outcome of this probe and increase uncertainty in an already divisive time," Buck wrote. 

Fox News' Brooke Singman, Caitlin McFall, David Spunt and Ronn Blitzer contributed to this report.