Washington (CNN) Two more lawyers have declined to join President Donald Trump's legal team, a Chicago-based law firm said Tuesday, the latest attorneys to turn down an invitation to represent the President amid special counsel Robert Mueller's investigation.

In a statement, Winston & Strawn said attorneys Dan Webb and Tom Buchanan "were unable to take on the representation due to business conflicts."

"However they consider the opportunity to represent the President to be the highest honor and they sincerely regret that they cannot do so. They wish the President the best and believe he has excellent representation in Ty Cobb and Jay Sekulow," the statement continued.

It is at least the fifth major law firm to receive a recent invitation to help Trump during Mueller's investigation into the 2016 campaign's dealings with Russia. Other lawyers who declined to join Trump's team include former US Solicitor General Ted Olson; Emmet Flood, who's worked for multiple presidents; Robert Bennett, Bill Clinton's attorney in the Paula Jones litigation; and Bob Giuffra, of Sullivan & Cromwell.

Last week, the lead lawyer on Trump's personal legal team, John Dowd, resigned amid disagreements with the President and increased scrutiny in the probe. And days after announcing that Joe diGenova and Victoria Toensing, a veteran Washington husband-and-wife duo, would represent him, Jay Sekulow, a lawyer for Trump, said Sunday that conflicts prevented the two from doing so.

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