President Trump claimed Thursday that his approval rating would be 75 percent if it wasn't for special counsel Robert Mueller's Russia investigation.

"Without the phony Russia Witch Hunt, and with all that we have accomplished in the last almost two years (Tax & Regulation Cuts, Judge's, Military, Vets, etc.) my approval rating would be at 75% rather than the 50% just reported by Rasmussen," Trump tweeted.

Trump blasted Mueller's probe as "Presidential Harassment!"

The president's approval in the Rasmussen poll is higher than most other surveys. Gallup's tracking poll showed Trump's overall approval this week stands at 40 percent.

Trump's message is the latest example of him venting frustration over the increasing pace of developments in the Russia investigation.

Mueller released a memo this week detailing former national security adviser Michael Flynn's extensive cooperation with investigators and is expected to file similar documents on Trump's former personal lawyer Michael Cohen and former campaign chairman Paul Manafort, both of whom have pleaded guilty to criminal charges.

Some legal observers have speculated the developments signal the investigation is moving closer to Trump's inner circle.